'Xi-nv'ti^Lv^/^^.^K^'C^ 



J. M. RUSK, 



c/ecle/ai^ o/ (S^ai€'ciim/ie. 



LIBRARY OF CONGRESS. 

PRESENTED BY 



UNITED STATES OF AMERICA. 



\ 



U. S. DEPARTMENT OF AGRICULTURE. 

HOG CHOLERA: 



ITS HISTORY, NATURE, AND TREATMENT, 



AS DETKimiXED BY 



THE INQUIRIES AND INVESTIGATIONS 

THE BUREAU OF ANIMAL INDUSTRY. 



WASHINGTON: 

GOVERNMENT PRINTING OFFICE, 
1889. 

15612 H 0—1 ^^-^i^ ^ 



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TABLE OF CONTENTS. 



Pago. 

Introduction and Spread of Hog Cholera in the United States 9 

Investigation of Swine Diseases 14 

Sympto:\is and Post-mortem Appearances in Hog Cholera :5:> 

'^.vsions produced hy hog cholera 34 

(a) Acute type :U 

(b) Chronic forms 3r> 

Hlstory and Autopsy Notes of ax Outbreak of Hog Cholera 37 

Disease in Healthy Pigs Caused by Material from this Epizootic... 50 

Brief Summary op tiii^ Important Features of this Epizootic 52 

Heramorrliagic lesions 52 

Ulcerative lesions 53 

Complications 54 

Lung lesions 54 

Bacteriological Observations 58 

The Causation or Etiology of Hog Cholera 03 

The bacillns of hog cholera 03 

Staining of hog-cholera bacteria 05 

Biologj" of the hog-cholera bacillus 06 

((() Diagnostic characters 66 

(b) Other physiological characters 69 

The Diagnosis os- Hug Cholera by Means of Inoculation 63 

Vitality of Hog-Cholera Bacilli and their Resistance to various 

Destructive Agexts 75 

Resistance of hog-cholera bacteria to heat in liquid media 75 

Vitality of hog-cholera bacteria in otdinary water 75 

Resistance to continuous drying at ordinary temperatures 78 

Some E.yperimknts on thk length of time during which Hog Chol- 
era Virus re.mains alive in the soil 80 

A few Additional Observations as to the A^itality of Hog Cholera 

Virus in the soil at the Experiment Station 8G 

The Effect of Some Disinfectants on the Virus of Hog Cholera... 87 

Mercuric chloride , 88 

Carbolic acid 88 

Iodine water 89 

Permanganate of potash 89 

Mercuric iodide 89 

Snlphate of copper 90 

Hydrochloric acid 90 

Chloride of zinc 90 

Sulphuric acid 90 

Crude carbolic acid 91 

3 



Page. 

Ordinary Lime as a Disixfectaxt fou Hog Cholera 93 

Disinfection of the soil with lime 99 

Is THERE ANV RESISTANT SpORE STATE IN THE LiFE HiSTOUY OF THE BA- 
CILLUS OF Hog Cholera 101 

Ways in which Swine become Infected 105 

By way of the digestive tract 105 

a. Fcediug diseased viscera 105 

1). Feeding pure culture of Hog Cholera bacilli 107 

Subcutaneous inoculation 109 

lutra-veuous iuoculatiou r Ill 

Infection by way of the lungs 112 

Some Observations on the Pathological Action of Hog Cholera Bac- 
teria 113 

Bacteriological Investigations of Hog Cholera in Nebraska, Illi- 
nois, and Maryland IIC 

Differential Characters of the Hog Cholera Bacillus 119 

Bacillus from Nebraska 119 

Bacillus from Illinois.. 119 

Bacillus from Maryland 120 

REL.4.TION of Hog CiJOLERA TO THE PUBLIC HEALTH 120 

Prevention of Hog Cholera 123 

Isolation, Disinfection, and Cleanliness as Prevextive Measures — 123 

Treatment of Hog Cholera 135 

experi.ments on the prevention of hog cliolera by inoculation 139 

I. Iuoculatiou of small doses of strong virus in the form of liquid culture.. 139 

II. The effect of feeding small quautities of cultures on inununity 151 

III. Injection of sterilized culture liquid to produce immunity 154 

Tests with sterilized cultures on pigeons 155 

Tests with sterilized cultures on pigs 159 

Experiments on the Attenuation of the IIog Cholera Bacilli by Heat 167 

Hog Cholera or Diseases closely Allied to it in other Countries .. 173 

In Great Britain - 173 

In Sweden and Denmark li^l 

In France 1>^C 



ILLUSTRATIONS, 



Page. 
Invkstigation of Hog Choleka: 

Plates I, II, III, aud IV. Illustrating necrosis and ulceration of the mu- 
cosa of the large iutestine, more particularly the cajcum 194 

V. Showing ulcers in the ileum 194 

VI. Showing hemorrhagic kidney 194 

VII. Showing hemorrhagic lung 194 

VIII. Showing hemorrhagic heart 194 

IX. Collapse and hroncho-pneumonia 194 

X. Microscopic characters of hog cholera bacilli 194 

XI. XII. Growth of hog cholera bacilli in various culture media.. 194 

XIII. Spleen aud liver of rabbit inoculated with hog cholera ba- 
cilli 191 

XIV, XV, XVI. Photomicrographs of hog cholera bacilli, showing 
variation due to growth in ditfereut media 194 

5 



LETTER OF TRANSMITTAL. 



Washington, D. C, January 18, 1889. 

Sir : I have the honor to submit herewith a report upon the history 
nature, and treatment of the disease known in the United States as 
hog cholera. Our linowledge of this pest has been developed almost 
entirely by the inquiries and experimental investigations of the Bureau 
of Animal Industry; and while much of the information contained in 
this volume has been published in the reports of the Department of 
Agriculture, a systematic and complete statement of the facts has never 
before been made in a connected manner. 

It has been discovered in the course of these investigations that there 
are two very different and distinct epizootic diseases of swine in this 
country which are widely prevalent, and which had previously been 
spokeu of under the one name of hog cholera or swine plague. Tliese 
two names had, therefore, been used synonymously i)revious to 1886, 
when the differences between the diseases were pointed out in there- 
ports of this Bureau. It was then deemed best to apply the term hog 
cholera to that disease in which the intestines were found most af- 
fected, and in which the symptoms would come nearest to justifying 
the appellation. The other malady appeared identical, not only in 
symptoms and lesions but in the microbe which caused it, with the 
disease recently described in Germany by both Loffler and Schiltz un- 
der the name of Schweineseuche, or swine plague. For this reason it 
was considered best to call this affection swine plague in the reports, 
and thus preserve uniformity and prevent confusion of ideas in refer- 
ence to the diseases of swine in different countries. 

This volume treats exclusively of hog cholera, as it is the malady 
which has been longest under investigation ; but the material is on hand 
for an almost equally complete volume on swine plague, which we hope 
soon to submit for j)ublication. There are, of course, aiany other dis- 
eases of swine, some of wdiich are communicable in a certain degree, 
but none of which are so widespread and fatal as the two that have been 
named. Some of these, especiall3' the parasitic ones, are receiving at- 
tention, and may in the future be treated at length in the bulletins of 
this Bureau. 

The greater part of the detailed study of the disease, the planning of 
exx:)eriments, and the bActeriologic^l investigations have been carried 

7 



8 

out by Dr. Theobald Smith, while the couducting of the experimeuts, 
the care of the experimental animals, and the general management 
of the experiment station have been under the direction of Dr. F. L. 
Kilborne. I can only speak in the highest terms of the untiring in- 
dustry and skill displayed by both of these gentlemen. 

The experiments in regard to prevention and medical treatment are 
being continued, but it is confidently believed that an understanding of 
the facts detailed in this volume will enable the owners of hogs to pre- 
vent or even arrest the great majority of outbreaks. It should be un- 
derstood, however, that the measures indicated must be enforced 
promptly, energeticallj', and thoroughly. 

D. E. SALMON, 
Chief of the Bureau of Animal Industry. 

Hon. Norman J. Colman, 

Commissioner of Agriculture. 



THE INTRODUCTION AND SPREAD OF HOG CHOLERA IN THE 

UNITED STATES. 



In the early days of bog-raising in the Uuited States these animals 
were comparatively free from disease, and wide-spread epizootic mala- 
dies among tliem appear to have been unknown. A circular letter of 
inquiry was recently sent from the Bureau of Animal Industry to the 
correspondents of the Department and to swine-breeders in all parts of 
the country, asking the date of the first appearance of hog cholera in 
the respondent's county, and a statement as to the health of swine pre- 
vious to that time. More than a thousand replies have been received, 
many of them so carefully written as to be of much interest and value. 
Nearly all agree in stating that at one time the swine industry was not 
subject to the ijeriodical losses from epizootics which now cause such 
discouraging losses. From the first appearance of this class of diseases 
the outbreaks became more numerous and more widespread until nearly 
all parts of the country are now subject to frequent invasions. 

The correspondence on this subject can only be briefly summarized 
in this bulletin. The first outbreak of disease supposed to be cholera 
that was referred to occurred in Ohio in 1833. It is reported from one 
county in South Carolina in 1837, and from one in Georgia as having 
existed in 1838. It existed in 1810 in one county in Alabama, one of 
Florida, one of Illinois, and one of Indiana. In 1813 it is reported from 
one county in [North Carolina. In 1811 one county in New York re- 
ports being affected. Its presence in 1815 is only mentioned by one 
correspondent from Kentucky. 

The thirteen years, from 1833 to 1815, inclusive, form a period in 
which but ten outbreaks of swine disease, supposed by the writers 
to have been hog cholera, were mentioned in these replies. It is evi- 
dent that during this period hogs were generally healthy throughout 
the country, and that the losses from disease were not sufficient to at- 
tract very much attention. The nature of the disease referred to as 
existing so long ago may, of course, be questioned at this day, and we 
have no means of deciding whether or not any particular outbreak was 
cholera or some non-contagious malady due to local conditions. It is 
reasonable to conclude, however, that the correspondents are correct in 
their opinion in most cases, because since 1815 the outbreaks mentioned 
became more numerous year by year until we fiud nearly the whole 

9 



10 

country involved. This rapid increase of the number of affected sec- 
tions would seem to indicate that a contagious disease had been intro- 
duced and carried to wideh^ separated sections of the country, from 
which it extended until, with a year favorable to its propagation, we 
find a sudden and alarming increase. 

Turning again to the number of outbreaks reported, we find, in 1840, 
that there were two in Korth Carolina, one in Georgia, one in Illinois, one 
in Indiana, and one in Ohio. In 1847 four are given in Tennessee and 
one in Virginia. In 1848 we hear from it in one county in Illinois, two 
in Indiana, two in Kentucky, one in North Carolina, and one in Virginia. 
In 1849 it is mentioned as in one county in Indiana and in one county 
in Ohio. In 1850 we have accounts of three outbreaks in Georgia, one 
in Pennsylvania, one in Indiana, two in Kentuckj^, one in North Caro- 
lina one in Ohio, and two in Tennessee. In 1851 there were outbreaks 
in Illinois, Indiana, and Tennessee. In 1852 there were two reported 
in Illinois, two in Indiana, one in Missouri, and one in Ohio. In 1853 
it invaded two new counties in Illinois, two in Indiana, two in Kentucky, 
one in North Carolina, four in Ohio, two in Tennessee, one in Texas, 
and one in Virginia. In 1854 it appeared in one more county in Illi- 
nois, four in Indiana, five in Kentucky, two in North Carolina, two in 
Ohio, and one in Tennessee. In 1855 it is found in six counties in Illi- 
nois, five in Indiana, one in Kansas, four in Kentucky, one in Missouri, 
two in Teimessee, and one in Virginia. 

The number of outbreaks mentioned by correspondents, it will be 
seen, is not less than ninety-three for the ten years from 184G to 1855 
inclusive. As compared with the ten outbreaks reported for the pre- 
vious thirteen years this is an enormous increase. There can be little 
doubt that it was during the period from 1846 to 1855 that hog cholera 
became scattered over the country and fairly began that work of de- 
struction which has become so familiar to us in later years. 

Below will be found a tabulated statement of the replies from nearly 
eight hundred and fifty of our correspondents. The figures show the 
number of original hog -cholera infections reported for the different pe- 
riods from the first recorded appearance of the disease in this country 
to 1887. Of course there have been many counties infected within that 
time which are not referred to in these communications, but the large 
number that were mentioned gives as perfect an idea as can now be 
obtained of the development and spread of this contagion. It is to be 
remembered that the outbreaks mentioned are not secondary infections, 
but are the first outbreaks of the disease in the correspondent's local, 
ity, and in most cases the first which occurred in his county. In nearly 
all cases it is stated that previous to the outbreak referred to the health 
of hogs had always been good, and the losses from disease had been 
confined as a rule to a single animal at a time. 



11 

Xumber and dates of original infections wiUi hofj cholera and swine pUujue, as compiled 

from recent correspondence. 



States. 


2 

a 

H 


-* 
H 








s 




(-1 • 


(0 




1 


1 


4 
2 


7 

7 


5 

1 


4 


1 
2 


1 

2 














? 


















1 

1 
3 

1 
1 
3 
13 
26 
3 
1 


1 


















1 














1 
1 
4 
8 
5 
11 
5 


3 

4 
17 
12 


1 


Plorida 


1 

1 
1 
1 






1 

13 
14 

8 
15 

7 
3 


7 

10 
11 

4 
3 






5 
14 
19 


i;i 

40 
20 
7 
2 

18 
2 




1 














3 






1 
15 


6 




1 


? 






1 
1 


















1 


2 

1 






3 
2 
3 




1 














? 














2 
1 

1 
8 
3 


't 














1 

8 
2 










4 
6 

1 


2 

8 


3 
Iti 

1 


2 
2 
15 

1 

2 

1 
1 
3 




? 






2 


1 






•^ 
















2 


1 










1 




1 
1 




1 
9 










7 


4 


10 


3 


4 








Ohio 


1 


11 

1 

1 

12 


7 
3 
3 

18 


c 

2 

1 
10 


9 

5 


12 
2 

1 


7 
4 




f) 




I 




1 












1 


Texas 




2 
8 


4 

4 
4 


5 
1 
13 


9 






4 


2 

•2 
1 


5 

2 


3 

4* 

1 


•1 






1 








"^ 











Whether the outbreak which occurred in Ohio in 1833 was the first 
introduction of hog cholera in this country or not, can not now be de- 
termined. It seems reasonably certain, however, that the contagion 
was imported from Europe with some of the animals that were brought 
from there to improve our breeds of swine. The investigations made 
in England and on the continent during the last year demonstrate that 
the swine fever of Great Britain is identical with our hog cholera, and 
that this disease is also widely scattered over the continent of Europe. 
This l)eiug the case, it would appear much more likel}' that the conta- 
gion was imported from there, as we know occurred with the contagion 



12 

of pleuro-pueumouia of cattle, than that it appeared spontaneously or 
was developed by tbe conditions of life in this country. Having been 
once introduced it spread gradually, following the lines of commerce 
and being for a long time confined to them, until, extejiding step by step, 
it has at one time or another invaded every section of the country in 
which swine raising is a prominent industry. 
Dr. George Sutton of Aurora, Ind., in 1858, wrote as follows: 

I have seen notices of this disease prevailing in the States of Illinois, Kentucky, 
Indiana, Ohio, New York, Massachusetts, Pennsylvania, and Maryland. It has pre- 
vailed extremely in Indiana, particularly in Dearborn, Ohio, Ripley, Rush, Decatur, 
Brown, Bartholomew, Shelby, Johnson, Morgan, Marion, Boone, Posey, and Sullivan 
Counties. It has also prevailed in Campbell, Kenton, Boone, Gallatin, Carroll, Breck- 
inridge, Bullitt, Bath, Henry, Henderson, Nicholas, Livingston, Union, and Crittenden 
Counties, Kentucky. It has also prevailed in Hamilton, Butler, Clinton, Fayette, 
and Clermont Counties, Ohio. Also in different portions of Illinois, and very severely 
in Wayne, White, and Gallatin Counties. It has also prevailed in the State of New 
York. The Ohio Farmer for January 3, 1857, quoting from the Buffalo Republic the 
extensive prevalence of the disease, says that "in western New York especially we 
learn it has been very fatal, but is now over. In conversation with one of the most 
extensive dealers in the neighborhood, a day or two since, he informs us that about 
six weeks ago he lost about four hundred in a very short space of time. A distiller 
in Jordan, during the month of September, lost fourteen hundred, which cost, in ad- 
dition, over $1,000 to have them buried. In Rochester, at all the i^rincipal points, 
and even among the farmers, the mortality has exceeded anything ever before heard 
of. A butcher in this city not long since purchased $500 worth of fat hogs, but they 
died so rapidly on his hands that he scarcely realized $75 on the investment." The 
Worcester (Mass.) Spy reports that many farmers in that city and vicinity are losing 
their swine by the mysterious and fatal disease known as the hog cholera. In the 
southeast part of the town it prevails in a greater or less extent upon nearly every 
farm. 

In most cases the disease is traced to Western hogs that have been sold by the 
drivers the present season, and which seem to have communicated the contagion to 
the other inmates of the sties in Vv'hich they have been kept. It is known that of 
many droves of Western shoats that have been sold at Brighton this season, and ped- 
dled about the State, nearly all have died. The disease has, no doubt, prevailed ex- 
tensively in other parts of the country, of which I have seen no notice. In this sec- 
tion of the country it has been extremely fatal. Over jiortions of Dearborn County 
it spread from farm to farm, and some of our farmers lost from 70 to 80 out of 100 of 
their hogs. At the distilleries the mortality has been very severe. I received infor- 
mation that more than 11,000 died at the distillery in New Richmond, in the summer 
and fall of 1856. The owners of the distillery at Aurora inform me that they have 
lost between C,000 and 7,000. A gentleman informs me that ho lost in 1856, at Ingra- 
ham's distillery, in Cincinnati, from the 1st of August up to the 24th of October, 
1,285, losing 1,152 out of a lot of 2,408. Another gentleman informs me that at the 
distillery in Petersburgh, Ky., he lost from the 1st of Juno up to the 18th of October, 
1856, 2,576. I have also received information from several other distilleries where 
the losses were large.* 

According to Dr. Sutton, this disease first appeared in Dearborn 
County, Ind., in July, 1850. 

* George Sutton, M. D., Observations on the supposed relations between epizootics 
and epidemics, and experimental researches to ascertain the nature of the recent epi- 
zootic among the swine, and the effects which diseased meat may have on human 
health. The North American Medico-Chirurgical Review, May, 1858, pp. 483-504. 



13 
Dr. E. M. Snow writes that — 

During the last five years this disease lias beeu seeu, from time to time, iu portioDS 
of the more eastern States, sometimes, as iu western New York iu 1856, proving quite 
severe and fatal iu comparatively limited localities. But in the Eastern States it has, 
to a great extent, originated Avith and has generally been coufiuedto hogs imported 
from the West. I think that iu no State east of Ohio has the disease prevailed ex- 
tensively, or attained the character of a wide-spread epidemic. 

In the vicinity of Providence, R. I., it has prevailed to some extent, more particu- 
larly among large herds of swiue during each of the last five winters, but has been 
mostly confined to hogs brought from the West, and has usually disappeared with the 
approach of warm weather. During the last winter it was more severe than iu any 
preceding, and was not confined to Western hogs. Neither did the disease, as here- 
tofore, cease with cold weather, but it continued until August, having destroyed 
more than 500 hogs in Providence and iu the adjoining towns during the first seven 
months of the present year, 1861. I havealso heard of its prevalence in various towns 
in Massachusetts during the same i)eriod.* 

The losses from hog cholera in the United States have been enormous. 
Estimates have from time to time been made from carefully-compiled 
data, and these have, so far as the writer is aware, never beeu less than 
$10,000,000, and have reached $25,000,000 annually. The inclusion of 
losses from other diseases is, however, unavoidable iu such estimates, 
and consequently some allowance must be made for these. The recent 
identificatiou of an epizootic pneumonia of hogs bj- the Bureau of Ani- 
mal Industry, a disease which appears to be identical with the kSchivelne- 
seuche of German writers, shows that the varieties of swine diseases in 
this country are more numerous than has beeu supt^osed. The erysipe- 
las of Europe (French, rouget ; German, Eothlaiif), and cliarbon have 
not yet been ideutifled as occurring in an epizootic or enzootic form 
among swiue in the United States but the existence of these diseases is 
not impossible, as the investigations have not yet been sufiQciently nu- 
merous to reveal the nature of all such outbreaks. The diagnosis of 
such diseases has been very uncertain in the past, because the symp- 
toms were not clearly defined, and not always sufiQciently characteristic. 
The most reliable means of discrimination between these maladies at 
present is the isolation of the microbes which produce them. The char- 
acteristics of these organisms are now so well knowu that the bacteri- 
ologist has no difficulty in distinguishing between them. 

* Edwin M. Snow, M. D., Hog Cholera. Annual Report U. S. Department of Agri- 
culture, 1861, p. 147. 



THE INVESTIGATIONS OF SWINE DISEASES. 



Among the first to investigate these diseases in the United States 
from a medical point of view was Dr. George Sutton, of Aurora, Dear- 
born County, Ind. In the extensive epizootics which prevailed in that 
county from 1850 to 1858 he had abundant material for study, and he 
noted the more salient features of the plague in a very clear and com- 
prehensive manner. While it is extremely difficult at this day to de- 
cide whether the outbreaks studied by Dr. Sutton were hog cholera or 
swiue-plagiie, or a combination of the two, his observations are very in- 
teresting and bring out many important facts. Of the syraptoniis, post 
mortem appearances, and nature of the mahidy, he says : 

This disease preseats a great variety of symxitoms. la January, 1856, wlieu tliis 
epizootic was at its height iu this section of country, I published a short notice of it 
in the Cincinnati Gazette. The symptoms which I then described I have found upon 
a more extensive observation to be correct. The hog first appears weak, his head 
droops, and sometimes iu a few hours after these symptoms diarrhea commences. 
There is frequently vomiting. In some cases the 'discharges were serous and clay- 
colored, sometimes dark, also bloody, and mucus resembling those of dysentery. The 
urine at first was generally small in quantity and high colored, but as the animal re- 
covered it became abundant and clear; this was one of the symptoms by which the 
men who were attending the hogs at the distillery ascertained that they were recover- 
iug. 

In a large number of cases the respiratory organs appeared to be principally af- 
fected ; there was coughing, wheezing, and difficult respiration. In some instances 
the animal lost the power of squealing, and the larynx was diseased. There was 
frequently swelling of the tongue and bleeding from the nose. In those cases where 
the respiratory organs were the principal seat of the disease there was generally no 
diarrhea or dysentery. In many instances the disease appeared to be principally con- 
fined to the skin ; sometimes the nose, the ear, or the side of the head were very much 
inflamed ; the ear swollen to twice its usual thickness. This inflammation would sjiread 
along the skin, sometimes over the eye, producing complete blindness. Sometimes 
one or more legs were inflamed and swollen, and the inflammation also extended 
along the body. The skin where w as inflamed was red and swollen. Some had 
large sores on their flanks or sides from 3 to 6 inches in diameter. Iu one instance, at 
the distillery, the inflammation extended along the fore leg, the foot became ulcerated 
and sloughed oft, and the animal recovered. Some appeared delirious, as if there was 
inflammation -of the brain. I examined the blood of four hogs which had this disease 
well marked; they were stuck, and the blood, arterial and venous, was caught in a 
bowl. It was cupped and presented a well- marked huffy coat. Death took place in 
from one to ten days after the attack. Sudden changes in the weather, particularly 
from warm to cold, appeared to increase the fatality of this disease. The average 

14 



15 ■ 

mortality of lioga that were iu pastures or fed ou slop was from 33 to 45 per cent., 
but it was frequently mucli more fatal if hogs were fed on corn — iu some instances 
ranging from seventy to eighty out of the hundred, and in some instances even 
higher. 

I found on opening the bodies of hogs that had died of this disease that they all 
presented evidences of a diffusive form of iullammation. From sixty-seven hogs that 
I have examined I found it was not confined to any particular tissue. Sometimes 
this inflammation was conlined to one organ; iu other cases it attacked several at 
the same time. The skin frequently presented jiatches of inllaumiation, and often 
had a purple appearance. In cutting through parts that were the most inflamed, the 
skin was swollen and the cellular tissue was infiltrated with serum. Frequently, 
however, the skin was merely discolored, without any swelling whatever. The 
stomach. was occasionally distended with food, and the mucous membrane in nearly 
every instance presented evidence of inflammation, sometimes extending over the 
whole stomach, at others only in patches. It was generally of a deeji-red color, 
thickened, and frequently softened. Sometimes it was covered with a viscid mucus.; 
in other instances there was an effusion of blood into the stomach. The mucous mem- 
brane of the snuill or large intestines, where there had been diarrhea or dysentery 
presented in all instances evidences of inflammation ; iu patches it was red, thick- 
ened, sometimes softened, and occasionally ulcerated ; where there had been dysen- 
tery there was generally bloody mucus found in the large intestines. The bladder 
generally contained urine ; sometimes its mucous membrane was inflamed, and iu one 
instance there was an efi'u^iou of Ijlood into this organ. In a large number of cases 
I found evidences of j)eritoneal inflammation, such as redness of this membrane, ef- 
fusion of turbid or bloody serum, adhesions between the intestines and between the 
intestines and sides of the body. In three instances blood was effused into the peri- 
toneal cavity — iu one instance more than a quart ; it appeared in this case to come 
from the liver. The liver was occasionally the seat of this inflammation, not only 
in its investing membrane, but the parenchyma ; sometimes there were abscesses, 
and in one instance portions of it were gangrenous. The lymphatic glands were gen- 
erally of a dark-red color, frequently resembling clots of blood. Tiiis disease of the 
lymphatic glands was of common occurrence. 

The lungs were frequently the seat of this inflammation, portions of one or both 
presenting difterent appearances, from simple congestion to complete hepatization ; 
sometimes there was ulceration, and frequently there was a turbid or sero-puruleut 
or bloody effusion into the i)leural cavity ; sometimes there were extensive adhesions 
between the lungs and pleura of the ribs. At first I was inclined to believe this 
malady to be a form of iileuro-pueumonia, but after I became better acquainted with 
it I found that the inflammation was not uniformly confined to any organ. In a 
number of instances the mucous membrane of the bronchia was deeply inflamed and 
the inflammation extended to the trachea and larynx. In several instances the larynx 
was inflamed, resembling laryngitis. One animal that had great dithculty in breath- 
ing and could make no noise I had knocked in the head, and on examination I found 
the mucous membrane of the larynx and epiglottis inflamed and swollen; also the 
tongue was swollen. There were evidences in several instances of pericarditis, which 
had produced adhesions between the heart and the pericardium. The brain, from the 
difficulty of opening the skull, Avas examined only iu one instance; it was found 
healthy, although I feel confident it was frequently the seat of the disease. 

From these examinations we sec ihafc it is a misnomer to call this malady cholera. 
It is a contagious inflammatory disease, the inflammation being confined to no par- 
ticular tissue, sometimes attacking only one, at others several, in the same animal. 
Evidences of this inflammation were found in the dermoid, the cellular, the serous, 
the mucous, and glandular tissues. I consider it a diffusive form of inflammation 
from the manner in which I have witnessed it spread along the skin. In one night I 
Jiave seen it extend from the eye to the ear— the ear becoming inflamed and swollen. 



16 

Altliougli we liave not been able to show that this is a cholera epizootic, still the facts 
elicited may be of interest and remove doubts at some future period. But, then, if 
this malady does not resemble cholera, does it resemble any of the diseases to which 
the human system is subject ? I think not. Like the specific eruptive diseases, it is 
highly contagious ; the infection has a period of incubation of from twelve to twenty- 
days, and one attack appears to exempt the animal from a second. But in this dis- 
ease, although petecchiic and an eruption may appear on the skin, its principal char- 
acteristic is a diffusive form of inflammation which may attack nearly every tissue 
and snread like an erysipelas. But then, again it differs from this disease, as it is well 
known that in erysipelas one attack does not exempt the system from a second ; and 
although erysipelas may be contagious, still it is doubtful whether the period before 
the eruption shows itself is so uniform as in this disease, and while erysipelas is gen- 
erally confined to tbe skin this inflammation most frequently attacks the lungs and 
mucous membrane of the alimentary canal. This disease appears to be intermediate 
between the specific eruptive diseases and erysipelas, partaking of the nature of each, 
and probablj'^ not having its exact resemblance among the diseases to which the human 
system is subject.* 

Of his experiments ami observatious ou the contagioustiess of the 
disease and the mauiier of its spread he writes : 

When the disease made its appearance in this section of country, iu the summer of 
18.'>0, and we saw it spreading from farm to farm, the question was .s\iggested whether 
it did not spread by contagion, for it was not known at that time (July) that the 
malady was contagious. Feeling much interest in watching the progress of this dis- 
ease, from the large numbers of animals that were dying, I suggested to the owners of 
the distillery at Aurora, Messrs. Graffs, that we should try a series of experiments to 
ascertain the nature of the disease, and whether it was propagated by contagion. 
To this they readily assented, and as they were constantly receiving fresh hogs, 
there was a fine opportunity to make any experiments we saw proper. I am indebted 
to Mr. J. J. Barkman, of Aurora, for seeing that the following experiments, with the 
exception of the last, were carefully made. The hogs on which the experiments were 
made were known to be healthy : 

(1) Six hogs that had been exposed to the malady by being in contact with dis- 
eased hogs were put into a yard by themselves and fed on slop and corn ; ou the four- 
teenth day from the time they were exposed to the disease they were all unwell ; 3 
died withiu a week afterwards, the rest recovered. 

(2) Ninety hogs were exposed to the disease, then put into a yard by themselves 
and fed on corn and water (no slop given) ; in thirteen days disease made its ap- 
pearance among them, and they continued to die until 60 out of the 90 died. 

(.3) Fifty hogs were put into a -pen by themselves, and fed on slop ; they had not 
been exposed to the disease ; for six weeks they continued healthy. 

(4) One hundred hogs that had not been exposed to the disease Avere put into a 
yard by themselves, and fed on corn and water; for thirty days no symptoms of dis- 
ease appeared among them. They were then, put into a pen with diseased hogs; on 
the thirteenth day they began to show symptoms of the malady, and the disease 
rapidly spread among them, until 40 died. 

(5) Thirty-three hogs, out of a lot of 2Q'3, were put into a pen by themselves ; for six 
weeks they continued healthy. The remaining 230 were put into a pen adjoining in 
which were diseased hogs; in thirteen days disease made its appearance among them, 
and continued until one-half died. 

(6) Four young andhealthy hogs were put into a pen in which, four days previous, 
diseased hogs had been ; they were fed on corn and water. On the fourteenth day 
they were all unwell ; and one died on the fifteenth day, and in five days more they 
were all dead. This experiment shows that the infection may be retained in a pen 
several days. 

* North American Medico-Chirurgical Review. 1858, II. 496, 



17 

(7) I inoculated, on the 28tli of October, five healthy hogs with the blood taken 
from the inflamed tissues of hogs that had died of this disease. On the fourteenth 
day (November 11) they were all unwell, and all died with the exception of one. 
In three inflammation spread from the point Avhere they were inoculated, along the 
skin and down the legs, which became very much swollen. I can not say that this 
inflammation was caused by the inoculation, for it did not appear until the fourteenth 
day, and many hogs had this external form of disease. 

From these experiments I think that we not only ascertained that this disease was 
infectious, but that the infection had a latent period of from twelve to fifteen days. 
Observations have since led me to consider the latent period as varying from twelve 
to twenty days. These experiments also showed that the hogs in the pens were not 
dying from strychnine in the slop. A statement was going the rounds of the papers 
about this time that strychnine was used in making yeast at the distilleries, and was 
poisoning the hogs at these places in large numbers. 

The manner in which this disease in many instances spread among hogs from farm 
to farm also showed most conclusively that it was infectious. One farmer had 75 
hogs that he turned into a corn-field to fatten. These hogs had been exposed to the 
disease, had become sickly, and numbers had died. He bought 36 more; these were 
all healthy ; they were put into the same field with the diseased hogs ; in two weeks 
they were unwell, and numbers died. He bought 4.5 more, all healthy, and put them 
in the same field; in two weeks they began to show symptoms of disease, and in a 
few days after a number died. Finding that he was likely to lose all his hogs, he 
sold 50 of the fattest that were left to the butchers in Cincinnati, at a reduced price, 
as diseased hogs. These hogs, it was said, were purchased for their fat, to be used 
in the manufacture of lard oil. After deducting the 50 he sold, he lost out of the 
156 all but 10. 

A large number of facts could be given, if necessary, to show the contagiousness of 
the disease. Hogs that had been once under the influence of this lualady appear not 
to be susceptible to a second attack. Although placed in pens with diseased hogs 
they continue healthy and fatten, and not a single instance can I find of hogs having 
this disease twice. There is reason to believe that this malady occasionally prevails 
at the distilleries in a mild form, as the old hogs at many of these places did not take 
the disease. But why it should suddenly have assumed so malignant a character is 
as difiicult to account for as that scarlatina, from being at one time the mildest of dis- 
eases, at another becomes one of the most malignant. On the farms the old and young 
bogs appear to be equally susceptible to the disease. 

la 1861 Edwiu M. Suow, M. D., of Providence, U. I., contributed a 
j)aper on bog^ cholera to the Annual Eeport of the United States De- 
partment of Agriculture (pp. 147-154). The symptoms of the disease he 
gives as follows : 

The symptoms, as described by persons unaccustomed to such observations, are ex- 
tremely various. By combining the information obtained from others with results of 
our own observations the symptoms, as seen during the life of the animal, are nearly 
as follows : 

(1) Refusal of food. — This is the first symptom usually noticed by those who have 
the care of the animals, though, as will be seen hereafter, this sympton by no means 
indicates the beginning of the disease. The refusal of food, after it is first noticed, 
generally continues through the whole sickness, and food of every description is 
mostly refused. 

(2) Great thirst. — This is constant, and large quantities of cold water will be swal- 
lowed if it can be obtained. Even after the animal is unable to stand alone it will 
drink cold water with eagerness. 

(3) After a time, the length of which varies very much, the animal begins to show 
signs of weakness; reels, staggers, and, iu attempting to walk, often falls down. 

15612 H C- 2 



18 

(4) In most cases there is a diariliea, with copious fluid discharges of dark, bilious, 
and very offensive matters. In a few cases there is no diarrhea, but evacuations of 
hard blacli balls ; but in some of these cases the fluid offensive matter is found in 
the intestines after death. 

(5) In a few cases there is vomiting ; but this is not often severe, nor is it contin- 
uous for any length of time. 

(6) The external appearance of the animal is at first paler than usual, but towards 
the last of the sickness purple spots appear, first on the nose and sides of the head. 
These extend along the sides of the belly and between the hind legs, after which the 
animal soon dies. 

(7) In many eases, perhaps a majority, ulcers are found on the different' parts of 
the body. These were particularly noticed on the inside of the lips and gums, and on 
the feet, and were often quite deep and excavated. In some cases these ulcers were 
seen in the nostrils, and in one case there were extensive ulcerations in the back part 
of the mouth, on the tonsils. 

(8) In some cases the legs are swelled, and the animal is lame ; sometimes the ears 
and sides of the head are swelled and red ; sometimes the eyes are sore and inflamed ; 
sometimes swellings like carbuncles are seen; and, generally, the glands near the 
surface seem to be enlarged. 

(9) In most cases the pulse is quickened, the breathing is hurried and difficult, and 
there is much cough. But in some genuine cases there is no perceptible trouble with 
the lungs, and no important signs of disease are found in them after death. 

(10) The duration of the disease in fatal cases, after the first symptoms are noticed, 
is extremely variable. We have seen some which have died within two or three 
hours; others have lived many days. It is difficult, however, to fix the time of the 
appearance of the first symptoms. The first noticed is usually the refusal of food; 
but it is probable, indeed it is certain, that the sickness is in progress for a consider- 
able period before the animal refuses food. Cases like the following are sometimes 
seen : A hog reftses to eat ; it soon grows weak ; staggers in walking ; turns purple 
on the sides and belly, and dies within two or three hours after the first symptom is 
noticed. But, on examination after death, extensive disease is fouiid in the intes- 
tines, or in the lungs, or in both, at a stage of development which must have required 
many days to reach. 

The ^os^morfew appearaDces are then summarized in the following 
language : 

Having described the symptoms, as seen while the animal is living, I will now give, 
briefly, the appearances found on examination of the bodies after death : 

In the course of our investigations, during the last winter and spring, the bodies of 
nine hogs were carefully examined by Drs. G. L. Collins, J. W. C. Ely, and E. T, 
Caswell, of Providence, in the presence of several other physicians. A minute ac- 
count of each case was prepared by Dr. Collins, and published in the Transactions of 
the Ehode Island Medical Society for 1861. It will be sufficient for the objects of this 
paper to give a brief synopsis of the diseased appearances which were found in these 
examinations : 

Lungs. — Ivl two cases the lungs were healthy. In tlie remaining seven cases one or 
both lungs were more or less inflamed, having a liver-like appearance, called hepatiza- 
tion. In some cases the inflammation was more advanced, and the substance of the 
lungs was breaking down into a mass of disease. In all cases Avhere the lungs were 
inflamed there was also pleurisy, and the lungs were adherent to the walls of the 
chest; the inflammation of the lungs and the pleurisy together constituting true pleu-. 
ro-pneumonia. In two cases there were tubercles, or consumption in the lungs ; but thisi 
is not uncommon in hogs, and is not supposed to have any connection with the spe-. 
cial disease we are considering. 

Stomach. — The stomach and the small intestines were generally healthy. The, 
stomach was freqently distended with an offensive mixture of food, and iu one casft 



19 

the inner surface was ulcerated to some extent. In two cases worms were found in 
small intestines, but this was probably a merely accidental occurrence, and had no 
necessary connection with the disease. 

Large intcsiines. — The inner coat of the large intestines was generally inflamed and 
softened with ulcerations to a greater or less extent, and they were fretiuently so 
tender as to be easily torn witli the fingers. On account of their diseased condition 
their inner coat was frequently discolored. The inflammation and ulceration of these 
intestines are probably the priucij)al cause of the diarrhea in this disease. 

Kidneys. — These organs were, in every case, much more pale and yellow than 
natural; this condition was well marked. 

The live)- and Madder were generally healthy. In some cases water was found in 
the cavity of the belly and of the chest, and in the membrane surrounding the heart 
(heart-case). In two cases numerous minute purple spots were seen upon the mem- 
brane lining the walls of the belly. The urine was often changed from the healthy 
condition, containing albumen and other diseased products, not, however, noticeable 
to the eye. Ulcers upon the feet and in the mouth were often found. The brain was 
not examined, as there were no symptoms observed which seemed to indicate disease 
of this organ. It may be at times affected, but is probably more rarely so than the 
other organs of the body. 

Such are some of the most important appearances which are found on examination 
of the bodies of hogs which have died with this disease. It will be noticed that three 
of the diseased conditions I have described are prominent, important, and such as 
would bo readily recognized by the most ignorant observer. 

These are, first, the pleurisy and inflammation of the lungs; second, the iuflanima- 
tiou, ulceration, and softening of the inner coat of the largo intestines; and, third, 
the pale and yellowish color of the kidneys. One or more of these diseased condi- 
tions will be found in every case, and in perhaps a majority of cases they will all be 
found in the same animal. 

While Dr. Suow admitted the disease to be epizootic he did not con- 
sider it to be contagious. Indeed, he neither considered epizootic nor epi- 
demic diseases to be contagions, but, on the contrary, hekl that they 
were caused by (1) "an epidemic atmospherical poison," and (2) " the 
local conditions or circumstances adapted to receive and propagate the 
poison existing in the atmosphere." 

In 1875 Prof. James Law contributed a paper to the report of the 
Department of Agriculture giving his observations upon hog cholera, 
or " intestinal fever in swine," in. which he so completely embraces the 
knowledge of our swine epizootics as it then existed that his paper is 
here reproduced in full. It is as follows : 

Synomjins. — Typhoid fever, enteric lever, tyi)hus carbuncnlar fever, carbuncular 
gastro-enteritis, carbuncular typhus, pig distemper, blue sickness, blue disease, pur- 
ples, red soldier, anthrax fever, scarlatina, measles, diphtheria, erysipelas. 

Definition. — A specific, contagious fever of swine, characterized by congestion, ex- 
udation, ecchymosis, and ulceration of the mucous membrane of the intestines, and 
to a less extent of the stomach ; by general heat and redness of the skin, effaceable by 
pressure; by small red spots, complicated or not by elevations and blisters; by black 
spots and patches of extravasated blood on the integument, the snout, nose, eyes, 
mouth, and all other visible membranes, and on internal organs, iueftaceable by 
Ijressure and tending to sloughing; usually by licjuid and fetid diarrhea; and by a 
very high and early mortality. 

The malady has been long known to pig-raisers and pork-factors in the Old World 
and the New, but in veterinary works it has been mistakenly placed in the list of 
malignant anthrax affections, to which many of its lesions bear a striking resem- 



20 

blauce. Two iluglish works, piiblislied withiu the last year, repeat this time-lionored 
fallacy. To malignant antlirax it is allied by the altered condition of tbe blood, by 
tbe solution of the blood-globules, by the imperfect coagulation of the blood in many 
cases, by the occasional enlargement and congestion of the spleen, by the extrava- 
sation of the blood out of the vessels (petcchi:e) into the skin, mucous membranes, 
and internal organs, and by the dusk^^ hue of the eye, nose, etc. That it is essen- 
tially distinct is shown by the fact that its virus, so frightfully contagious and fatal 
to pigs, is not communicable to any other domestic animal. The contagion of malig- 
nant anthrax, on the other hand, is deadly to all domestic animals, and even to man 
himself. 

The common American designation of hog cholera has only the diarrhea to support 
itj and, as we see outbreaks in which this feature is mainly remarkable for its ab- 
sence, the name comes to be an absolute misnomer. In many cases a gelatiniform 
exudation takes place on the affected surface of the mucous membrane of the intes- 
tines, windpipe, or bronchia, and the disease has accordingly been named diphtheria. 
But as such an exudation is by no means constant, a name founded on this peculiarity 
would have no actual foundation in a large proportion of cases. Again, the exuda- 
tion (see Post mortem No. 1) is mainly composed of cells and granules, with less of 
the fibrinous matrix than is usual in diphtheria. Lastly, the intestinal fever of swine 
is most virulently contagious, whereas diphtheria is very slightly, if at all, infec- 
tious, and is confined rather to certain insalubrious localities or buildings. 

From scarlatina and measles it is sufficiently distinguished by the constancy of the 
intestinal legions, though it resembles both in its cutaneous rash. With erysipelas 
it has no real connection, the one common feature, the redness of the skin, being due 
to a condition altogether different in nature, progress, and results. 

The constancy of the congestion, specific deposit, and ulceration in the intestines 
in the fever of swine, characterize it as perfectly as do the same lesions in tyjihoid 
fever in man. It further agrees with typhoid. fever in having a higher evening than 
morning temperature and a rose-colored eruption on the skin. To this disease, indeed, 
it bears a closer resemblance than to any other disorder of man or beast, so that Dr. 
Budd and others with much plausibility call it the typhoid fever of pigs. But in 
spite of the similarity of the sj^ecific deposits and ulcerations on the intestines, those 
of the pig show less tendency to attack the agmiuated glands (Peyer's patches) and 
the solitary glands than is the case in man. They appear on all parts of the mucous 
membrane of the large and small intestines, yet the agmiuated and solitary glands 
rarely escape entirely, and sometimes they alone are the seats of ulceration and morbid 
deposit. The skin eruption, too, in the pig-fever is often distinctly raised, and even 
vesicular, whereas that of typhoid fever is a simple rash, and, like a blush, may be com- 
pletely though temporarily efiaced by pressure. Finally, the contagion is incompara- 
bly more virulent and tenacious of life than that of typhoid fever, and the mortality 
is greater and occurs earlier in the disease. On the whole, we must look on this 
aftection of pigs as a disease sui generis, having close afiSuities with the typhoid fever 
of man, yet essentially distinct, and hence the term intestiua' fever of swine is more 
applicable, as at once expressing its nature and avoiding confounding it with otlier 
and distinct affections. 

Inciibalion. — The period of incubation has not been definitely settled. My experi- 
ence in Scotland in 1864 would have led me to set it down at from seven to fourteen 
days. The infected jiigs were four days on the journey from the English market by 
rail and seven days on the farm before the disease manifested itself. Again, the 
home-bred swine were sound until four weeks after the strange hogs came on the 
farm, and three weeks after the latter were generally sick. Pigs, though farrowed 
by sick dams, did not show any sign of disease for about a week, although nearly all 
eventually died. 

In Dr. Budd's cases, in April, 18C5, the fir^t symptoms of illness were shown four 
or five days after the pigs were brought from Bristol market, where they may or may 
not have been infected. 



21 

Dr. Sutton'a experimeuts, made at Aurora, Intl., in Septoiiiber, October, aud Novem- 
ber, 1848, deserve repetition in this couneetion. (1) Six hogs, after contact Avith dis- 
eased animals, were placed in a sound pen, aud sickened on the fourteenth day. (2) 
Of 90, similarly expostd and then put in a sound yard, some sickened ou the thir- 
teenth day. (3) One hundred, similarly exposed, contracted the disease ou the 
thirteenth day. (4) One huudred and thirty, jihiced in a yard adjoining one occu- 
pied by diseased hogs, became ill on the thirteenth day. (5) Four young aud healthy 
pigs, placed in a pen occupied four days previously by diseased hogs, sickened on the 
fourteenth day. (G) Five healthy hogs, inoculated with the blood from the inllamed 
tissues of diseased swine, were unwell on the fourteenth day. 

Further experiments were made by Proftssor Axe, of London, in April, May, June, 
aud July, 1875. (1) Two healthy jiigs wei'c (in April) placed for forty-eight hours 
in the same house with a diseased one, contact being carefully avoided. One was 
dull and otf its food on the sixth day and the other on the eighth. (*2) Ou May 
15 a pig was inoculated with the liquid cutaneous exudation, which had been kept 
on dry ivory points for twenty-six days. On the fifth day there was slight dullness 
and heat of skin, aud on the sixth the malady was well developed. (3) Ou June 
10 another pig Avas inoculated with the cutaneous exudation of the last, the opera- 
tion being performed by another party and the i)ig kept apart to avoid all risk of 
indirect contagion. On the fifth day temporary redness was noticed on four teats, 
and on the sixth day the symptoms were fully developed. (4) Another pig broke into 
the pen occupied by the last-named subject and was left there for six days, when it 
was taken out seriously ill. In the hot summers of Illinois instances are met with in 
which symptoms of the disease are shown in a previously healthy herd under three 
days after the wind has blown from the direction of a sick lot half a mile distant. In 
analyzing this apparently somewhat discordant evidence we must bear in mind that 
the period during which a poison will remain latent in the system will vary accord- 
ing to the amount taken in, the excited or febrile condition of the subject, and the 
mode of introduction into the system. Thus an excess of any poison, animal or veg- 
etable, will usually show its etfects with remarkable rapidity. A feverish state of 
the system, whether induced by intense heat, passion, or disease will rouse the poison 
into unusually early activity. Lastly, poisons that are inoculated usually act sooner 
than those introduced into the system by other channels. These considerations 
will serve to reconcile the prolonged latency of the poison in Dr. Sutton's cases, 
observed in cold weather, as compared with Dr. Budd's, Professor Axe's, and my own, 
in the English summer, and of these in their turn with the iirorapt development of 
the malady in the semi-tropical summer of Illinois. 

Stjm])io7ns.— The earliest symptoms are slight dullness, with sometimes wrinkling 
of the skin of the face as if from headache ; shivering or chilliness and a desire to 
hide under the litter are not uncommon. Some loathing of food, intense thirst, 
elevation of the temperature of the rectum to 104° Fahrenheit and increased heat 
and redness of the skin are usually the first observed symptoms, and occur one or two 
days later than premonitory signs above mentioned. The increased heat of the skin is 
especially noticeable inside the elbow aud thigh and along the belly. By the second 
day of illness the whole surface feels hot, and in white pigs is suifused with a red 
blush, which may pass successively through the shades of purple and violet. It is 
usually more or less mottled at particular points, aud a specific eruption appears as 
rose-colored spots of from 1 to 3 lines in diameter, sometimes slightly raised so 
as to be jjerceptible to the touch, aud either pointed or more frequently rounded. 
The redness fades under the pressure of the finger, but only to re-appear immediately. 
The eruption is usually abundant ou the breast, belly, and haunch, the inner side of 
the forearm and thighs, and the back of the ears. It stays out for two or three days, 
and may be followed by one, two, or more successive crops of the same kind. The 
cuticle is sometimes raised in minute blisters, a feature which distinguishes this from 
the rash of typhoid fever, and the liquid of such blisters inoculated ou other pigs 



22 

communicates tlio disease. In addition to the rasli and simultaneously with it, or 
soon after, there appear on the skin numerous spots of a dark-red or black color, vary- 
ing in size from a line to an inch in diameter, on the color of which pressure has no 
etfect. These are due to the extravasation of blood or of its coloriiig matter from the 
blood vessels into the tissues, and they dry up into thiu scabs or slouglis if the ani- 
mal survives. Similar petccchial spots appear on the muzzle, in the nose, and oh the 
eyes, and in some instances they are confined to these parts. The tongue is covered 
by a brownish fur. 

From the first the animal is sore to the touch, but as the disease develops the handling 
of the animal is especially painful and causes grunting and screaming. The pig lies 
on its belly, and, if compelled to rise and w^alk, moves stiffly, feebly, unsteadily, 
and with plaintive grunting. This weakness aud prostration rapidly increases, and 
often ends in utter inability to rise or to support the body on the hind limbs. A wa- 
tery discharge from the nose, followed by a white muco-purulent flow, is not uncom- 
mon. A hard, barking cough is frequently present from the first and continues to 
the last. Sickness aud vomiting may be present, but are far from constant. The 
bowels are often confined at first, and in certain cases, and even in nearly all the 
victims of particular outbreaks, may remain so throughout, nothiug whatever being 
passed, or only a few small black pellets covered by a film of mucus. These cases 
are quickly fatal. More frequently, however, they become loose by the second or 
third day, and diarrhea increases at an alarming rate. The XJassages are first bilious 
and of a light or brownish yellow when not colored by ashes, charcoal, or the nature 
of the foo I. But soon they assume the darker shades of green and red, or become 
quite black aud intolerably offensive. In such cases the elements of blood, inspis- 
sated lymph, and membranous pellicles, sloughed off from the ulcerated surfaces, are 
usually to be found in them. 

The diarrhea becomes more profuse, watery, and fetid ; the pulse siuks so as to be- 
come almost imperceptible; the cough becomes more frequent, painful, and exhaust- 
ing; the breathing is more hurried aud labored; and the weakuess iucreases until 
the patient can no longer rise on his hind limbs. At this period the petecchite become 
far more abundant. Before death the animal is often snnk in complete stupor, with, it 
may be, muscular jerking or trembling, or sudden starts into the sitting posture, and 
loud screams. In the last stages involuntary motions of the bowels are common. 

Exceptionally swellings appear on the flank, with extreme lameness, aud extensive 
sloughs of the skin of the ears or other parts. Palpitations of the heart also occasion- 
ally occur as precursors, attendants, or sequels of disease. If the disease should take 
a favorable turn, slight causes maj' make an early and perfect recovery, a complete 
convalescence being established in three or four weeks. A considerable proportion 
of the survivors, however, linger on in an unthrifty condition for months, evidently 
suffering from the persistent ulceration of the intestines or infiltration of the lungs. 
The mortality often reaches 80 or 90 per cent, of all swine exposed, and in case of a 
certain number of the survivors recovery brings no profit to the owner. 

Post-mortem apjiearances. — The blue color of the skin becomes deeper aud more uni- 
versal a few hours ifter death. The fat beneath the skin is colored more or less 
deeply in points corresponding to the discoloration of the integument. The snout is 
usually of a deep bine, with ineffaceable black spots (petecchiai). The membrane 
lining the eyelid, -and to a less extent the skin, present similar black spots of extrav- 
asation. 

The most constant chauges are in the mucous membrane lining the alimentary 
canal, and especially that of the terminal portion of the small intestine (ileum) aud 
the commencement of the large (crecum, colon). The tongue is f nrred, but deep red, 
even eroded, at its base, and the pharynx and adjacent parts usually studded with 
petecchiiB. The cavity of the abdomen generally contains a few ounces of reddish 
serum, which coagulates on being heated. The stomach may show no more than a 
pink blush, but more commonly it is of a deep red, from congestion, especially to- 



. 23 

vrard tlie pylorus, and its mucous luembrane is oftcu black tbrotigliout from tbe close 
aggregation of petecchiaj. Tbe small intestines are usually extensively congested, 
and of a deep red, in many cases approacbing to black, as examined exteiually. 
Tbeir mucous membrane in such parts is equally bigb colored, studded with petec- 
cbiiip, and iu some cases lined by a firm, semi-fibrinous exudation. A more constant 
condition is tbe presence of minute slougbs or erosions in tbe seat of peteccbiie, and 
of equally small elevations, duo to excessive cell-growtb, l)eneatb tbo epitbelium. 
These commonly have a whitish center, with a yellowish or red border. Such is tbe 
appearance in cases that prove fatal within two or three days. In tbose that have 
survived longer, extensive ulcers appear, of au iuch and upward iu diameter, evi- 
dently the sequel of tbe petecchia>, and cspcciallj- of the eruption. 

These ulcers are often covered by black scabs or sloughs, have irregular projecting 
margins and a variously colored center, consisting of cells iu process of disiutegration. 
They are sometimes situated on Peyer's patches, but show no very marked preference 
for those over other portions of the mucous membrane. The large intestines present a 
similar varying vascularity, discoloration, peteccbiie, deposit, softening, and ulcera- 
tion. Tbe changes are especially marked iu the c;ecuui and colon and in the rectum 
close to tbe anus. The solitary glands are often large and open, but the ulcers show 
no particular preference for tbe points occupied by them. Extensive extravasations 
of blood into tbe coats of tbe bowels aud ani<ing their couteuts are not infrequent, and 
in certain exceptional aud advauccd cases tbe peritoneum is inflamed and false mem- 
branes bind the bowels together or to other organs, or to tbe walls of tbe abdomen. 

In tbe wind-pipe and air-passages within the lungs, the mucousmembrane is usually 
mottled with black petecchi;e, or covered by a viscid mucous exudation. The anterior 
lobes of the lungs are often soliditied by exudation, biit remain bright, red, tough, and 
elastic (^splenisation). Limited hepatization is also exceptionally met with, and even 
false membi-anes ou the pleura or pericardium. 

PetecchiiP are couamon over the various internal orgaus^ou the lungs, pleura, heart, 
pericardium, diaphragm, peritoneum, liver, pancreas, kidneys, and bladder. The 
spleen is large and dark, as is usual in connection with blood poisons. Both sides of 
the heart contain clots of blood, extending from the auricles and ventricles into the 
great vessels. In the worst cases, tbe clot is black, soft, aud somewhat diffluent; 
exceptionally it is firm, aud shows a distinct butty coat. The blood-globules, as seen 
under the microscope, are more or less puckered or crenated at their edges, aud mixed 
with an excess of granular debris aud even in some instances spores of a fungus 
(mia-ococcus). 

As illustrating tbe various lesions in different cases, I append from my notes of 
post-mortem examinations two that occurred with two years' interval, near Edin- 
burgh and London, respectively : 

I. — No. 4. A three mouths' old, white Yorkshire pig in excellent condition. Exam- 
ined a few hours after deatb, being still quite warm, rigor mortis bad set in strongly. 
Along the whole lower surface of the body, from the mouth to tbe tail, are spots of 
dark retf or purple. On the right side of tbe head and left side of the chest the spots 
run into each other, so much that they seem to form a single continuous blush. On 
tbe back the spots are smaller and less numerous. There are no spots nor iietecchiie 
on the snout, but a glairy bloody fluid runs from the right nostril. 

The membrane lining tbe eyelid is congested, having a dark hue, aj)proaching 
purple, and a portion of the mucous membrane of the rectum, exposed by the relaxa- 
tion of tbe sphincter, presents the same appearance. Dark red spots and peteccbite 
exist aboiit the vulva. Under the belly is a subcutaneous layer of fat about an inch 
thick, aud beneath the purple spots ou the skin this is discolored by blood through- 
out the entire thickness. 

The abdominal cavity contains (> ounces of a dark bloody fluid. The intestines 
have a deep florid hue externally. The stomach and the greater part of tbe rectum 
are pale and without any lesions of the mucous membrane. Close to the anus this 



24 

membrane is cougested. The stomach coutaius about two poumls of food (boiled 
potatoes, corn, etc.). The small iutestiues have their nincous membrane thickened, 
soft, friable, and very red, the shades being lighter or deeper at different points. It 
presents at intervals spots of a much darker hue, approaching purple, and respect- 
ively from one to two lines in diameter. The large Peyer's patch on the ileum seems 
hypertrophied and of a deerp red, especially close to the ileo-caical valve, where it 
also shows small ulcers. The large intestines have their mucous membrane of a very 
bright red, soft, friable, and presenting at intervals small ulcers of about a line in 
diameter, and corresponding apparently to the solitary glands. Some of these ulcers 
are of a deep red, and appear on the peritoneal coat as dark spots ; others are of a 
dirty white in the center, with raised red edges, and are not so marked on the perito" 
neal surface. A small nodule felt through the outer coats is characteristic of both. 
The contents of the large intestines consist of dark semi-liquid feces, with a great 
amount of ashes. 

The liver is variable in color and very friable. Though still warm, it presents 
small bubbles of gas at intervals under its capsule and throughout its substances. 
The gall-bladder is half full of a very light-colored yellow bile. The pancreas seem 
healthy. The kidneys, bladder, and uterus are normal. 

The pleura and lungs appear healthy, excepting a portion of the anterior lobe of 
the left lung, which is in a state of spleuisation. The bronchia contains bloody 
froth, especially in the left lung, and those of the solidified portion contain a white 
solid substauce, completely filling them, and appearing to the naked eye like a fibri- 
nous clot, while under the microscope it is found to be mainly composed of small glob- 
ules about the size of blood-cells. It is disintegrated and i^artly dissolved in a strong 
solution of potassa. The mucous membrane of the larynx and trachea is cougested 
and the tube filled with a white frothy mucus of an exceedingly tenacious consist- 
ency. 

II. — No. 2. Three months' old female pig, large of its age. Dead twelve hours. 
liigor mortis well marked. Skin almost universally of a livid hue, but pxirple along 
the abdomen. Back, white. Profuse eruption over the body, but especially abundant 
on the abdomen. The smallest, and evidently the most recent specimens of the 
eruption, are individually about a line in diameter, deep purple, and covered by a 
delicate, slaty-looking skin. The larger sjiots have a dark, hard, dead center, which 
appears to spread gradually to the whole of the jiatch ; some appear as a large black 
scab of one-half to 1 inch in diameter. 

Abdomen contains G ounces of serum, which forms a solid coagulum on being heated. 
False membranes bind the large intestines to the lower wall of the belly, also the 
two horns of the uterus together and to the bladder, and both to the walls of the 
pelvis. The large intestines are the seat of an exudation half an inch thick, from 
which a straw-colored fluid escapes on section. The stomach is considerably dis- 
colored on its great curvature externally, as if from extravasated blood. The mucous 
membrane of the stomach presents numerous petecchiie and ramified redness along 
the great curvature. The small intestines show slight branching redness o& part of 
the ileum. 

Large intestines. — Ctecum has its mucous membrane abnormally vascular; with 
abundant j^etecchiaj, and ulcers of considerable standing ; these appear as white, 
raised masses, and have no manifest connection with the solitary glands. The blind- 
gut contains numerous ascarides. The mucous membrane of the colon repeats that 
of the c£ecum, but at one point beneath its serous coat is a blood-clot measuring 1 
inch by half an inch, and a quarter of an inch thick. 

The liver is healthy. The diaphragm has abundance of petecchia? on its posterior 
surface, especially on the cordiform portion, and ajvparently leading in radiating 
lines from the center. Beyond the presence of petecchiie the organs of the chest seem 
to be little affected. 

Causes, — Contagion is the main cause of this disease. The introduction of diseased 



pigs into healthy herds ; the placing of healthy pigs iu pens, cars, steam-boats, mar- 
kets, etc., where diseased swine are then or have formerly been exposed; afresh 
breeze from the direction of a diseased herd, though half a mile distant ; the passage of 
men or quadrupeds or birds from the diseased to the healthy ; the use of food, litter, 
or water that has been in near proximity to the affected animals, have each served to 
transmit the tcver. 

The virus appears to be concentrated in the bowel-discharges and liquids of the 
eruptiou, but doubtless exists iu all the liquids aud tissues of the body, and is given 
oft' into the air from the skin and exposed mucous membranes. Pigs are often born 
sick, aud die in twenty-four hoars. The feeding-troughs aud water, contaminated by 
the (ilthy feet aud "snouts, are particularly liable to convey the disease. 

The n)alady prevails at all the periods of the year, but it has opportunities for the 
widest dift'usion iu dry seasons aud countries, where the virulent matter may be dried 
up and preserved unchanged for an indefinite period, and in this state may be car- 
ried by winds and otherwise. Wet weather contributes to the decomposition and 
destructiou of this, as of any other animal poison, but can not influence its propa- 
gation by the direct contact of healthy with diseased animals, nor affect its preserva- 
tion inside dry buildings. 

Unwholesome conditions of life contribute largely to its diffusion, if not to its de- 
velopment de novo. The malady frequently appears in pigs that have been carried 
several days in succession in crowded boats or cars, among the accumulated filth of 
their own bodies and those of their predecessors, and subject to compulsory absti- 
nence from food and water. Again, it will ocour in fat hogs that have been driven 
a number of miles under a hot sun and then cooped up iu a filthy, close, ill-ventilated 
pen, subjected to the reeking fumes of their own bodies and of long-accumulated 
uastiness. Many think that dry-corn feeding and overcrowding on filthy manure 
heaps are largely productive of the disease. But it is too much to assume that the 
poison is developed (7c )iovo in such conditions. Similar unwholesome influences favor 
the development of all contagious diseases by loading the blood with eftete and dele- 
terious organic matter, and bringing about a feverish and susceptible state of the 
system. But, on the other hand, such abuse and maltreatment fail, in very many 
cases, to induce the affection, so that we are left in doubt in regard to those instances 
in which it appears as to whether the virus was not hidden away in the buildings, 
cars, etc., and roused into activity by the presence of a fertile field for its growth in 
the bodies of the pigs, the blood of which was loaded with organic elements in proc- 
ess of decomposition. The important iioint is this: We know this as a contagious 
affection, to the propagation of which all probable insalubrious conditions contribute. 
So soon as we couceutrate our atteution on this point we have the key to its preven- 
tion, if not to its entire extinction. But, while admitting the iufluence of over- 
crowding, filth, starvation, and suffering iu predisposing to this disease, it ought to 
be added that the very highest mortality is often reached among pigs kept in the 
best hygienic conditions, but among which the virus has been accidentally intro- 
duced. Again, some hogs, and even families, appear to be insusceptible, and resist 
the j)oison which is carrying off all around them. But similar instances of immunity 
are met with in all contagious affections. 

Treatment. — In a fatal contagious disease like that under consideration it is rarely 
good policy to subject to treatment. The enormous iucrease of the poison in the 
bodies of the sick, aud the extreme danger of its diffusion through the air, as well as 
on the feet of men and animals, render the preservation of the victims eminently un- 
safe and unprofitable. Yet, iu the case of very valuable animals, and where seclu- 
sion, disinfection, and careful nursing can be secured, it may be resorted to. 

A dry, airy, well-littered building may be provided, abundantly spriukled with a 
solution of carbolic acid or chloride of lime. Rugs steeped in a solution of one or 
other of these agents may be hung up at intervals, and sulphurous acid set free by 
burning a piuch or two of sulphur three or four times a day. The dung should be 



26 

saturated or thickly sprinkled with fiuely powdered copperas. Auy drains will re- 
quire disinfection in the same way. If the sick animals are kept in tlie open air, the 
ground must he freely sprinkled with disinfectants, above all where the dung has 
been deposited. 

The diet should he well boiled gruel of barley, rye, or Graham ilour; or, if fever 
runs high and the temperature is raised by such food, corn-starch made with boiling 
water or milk may be substituted. Fresh, cool water should be freely supplied, either 
pure or slightly acidulated with sulphuric acid. 

During the early stages, while constipation exists, the bowels may be gently opened 
by castor oil (2 ounces for a good six-months' pig) or rhubarb (1 dram), aided by in- 
jectious of warm water. The heat of the skin must be counteracted by spongiug 
with cool or tepid water, as may seem most agreeable to the patient. As the laxa- 
tive operates, 20 grains of uitrate of potash and 10 grains of bisulphite of soda may 
be given twice a day in the drinking water. Charcoal may also be given to absorb 
aud neutralize the deleterious products in the bowels. Or the uiter may be replaced 
by any other neutral salt and the bisulphite by another antiseptic agent. If the pa- 
tient survives the first few days and gives indications of ulceration, by tender abdo- 
men, diarrhea, and the passage by the bowels of membranous sloughs, oil of turpen- 
tine, in doses of 15 or 20 drops, may be given, shaken up in milk or beaten in an egg ; 
or this nifiy be replaced by similar doses of creosote or carbolic acid, or 3 to 5 grain 
doses of uitrate of silver. It may he necessary to give opium to check excessive 
purging, or stimulants to sustain the failing strength and very prostrate condition. 
Infiltrations and intlammatious of the lungs aud bowels may demand applications of 
mustard aud turpentine to the chest or abdomen. In short, any complication must 
be combated as it appears, aud the soundest judgment will be wanted throughout to 
adapt the treatment to the various indications. Each case will demand as close at- 
tention and as careful an adaptation of remedial measures to its diii'erent stages and 
phases as would a case of typhoid fever in man. In case of recovery a course of tonics 
(gentian one-half dram, sulphate of iron 10 grains daily) will often be beneficial, and 
the return to ordinary feeding should he brought about by slow degrees. 

Prevention. — A successful system of prevention can only be instituted when we duly 
appreciate the fact that almost all cases of this intestinal fever are due to contagion. 
And this is precisely what our hog breeders fail to realize. No man in his senses will 
affect to deny that the disease is contagious, but the natural tendency is to seek for 
other causes in the great majority of cases. As in the case of all contagious affections 
that have attained a wide prevalence, this iiresents a number of outbreaks which can 
not be traced to contagion from any diseased stock, and these are at once assumed to 
be spontaneous, and the cause of the disease is sought in the peculiar treatment of 
the herd, aud future prevention is attempted by the avoidance of these peculiarities. 
In illustration, I may quote from a letter of Mr. I. F. Hatch, an intelligent lUiuois 
farmer, and former student of Cornell University : 

In former years hog cholera has been local with us except when it first appeared, 
some ten or twelve years since. Then, as now, it was general, aud swept everything. 
But since then it has been confined to a few farms or localities. Sometimes it ap- 
peared on a single farm, or perhaps on several farms, 1, 2, or 3 miles apart, all others 
escaping. I have a ueighbor who has had it every second year since its first apppear- 
auce, losing more or less hogs each time, but his is the only case of which I have been 
informed where it has been so regular and often. 

This irregularity and local appearance deluded us into the belief that we were pre- 
venting the disease by extra care and attention, and that salt, sulphur, aud ashes 
were a preventive ; but we have been eftectually undeceived this time, for hogs that 
have been doctored thus fared no better than those that had not. 

There is one man here whose hogs have escaped the disease entirely, and he has 
fed for a number of years once a week, or once in two weeks, corn boiled in the ear 
with ashes — lyedcorn, as they call it — putting a peck of wood-ashes into a 40-gallou 
kettle. He tells me he has had no cholera since he adopted this plan, and his hogs are 
certainly good subjects for cholera — poor, half-fed, and sleeping in a pile under the 
barn. He says others have tried this plan and successfully warded off the disease. 



27 

He goes ou to quote iustauces of .illegetl prevention byfeevliug house-slops ■without 
corn, and by giving once a week a feed of the boiled jowls and waste parts of the pigs 
killed the year previous, and adds: 

Generally diseased hogs run, sleep, and eat with the others, it being the general 
opinion that they'll all have it anyway, so no matter. I ani of a dilferent opinion. 
A few change the yards and sleeping places, but generally they stay in the same 
places throughout the disease. No attention is paid to disinfection. 

These alleged preventives are doubtless somewhat beneficial by maintaining a 
free action of the bowels and kidneys, and favoring the elimination of the poison, as 
does diarrhea in the milder cases of the disease. But there need be as little doubt 
that, like the salt,- sulphur, and ashes, they would all fail in the presence of a strong 
dose of the poison. Meanwhile, they are made to serve an evil purpose in diverting 
attention from the one etfectual means of restricting the disease, the extinction of 
the poison. It must be fully recognized that neither contact nor proximity is neces- 
sary to contagion. The poison may be carried a certain distance on a stream of water 
without losing its vitality. It may be blown a long way by a favorable wind, when 
dried, up, on light objects. It may be carried on the boots, hands, etc., of men 
(dealers) passing from farm to farm and from district to district. Horses, cattle, 
sheep, dogs, fowls, pigeons, and wild animals of all kinds are liable to carry the virus 
ou their feet and limbs, and to deal out death to the pigs at places widely separated 
from each other. It is, therefore, quite impossible to trace all new outbreaks to con- 
tagion. But to attribute them to spontaneous evolution of the disease is to beg the 
whole question. 

It can be freely conceded that a certain number of cases probably originate spon- 
taneously every year ; but these arc few and far between as compared with the enor- 
mous mortality caused by contagion. It can be equally conceded that certain seasons 
are far more favorable to the propagation and virulence of the disease than others, 
yet even in these the great uiajority of cases are infectious. It can be admitted even 
that a wholesome laxative diet is to some extent protective, as well as comfortable 
dwellings and antiseptic agents, like copperas, bisulphite of soda, charcoal, or car- 
bolic acid. But all .such protectives are comparatively limited in their operation, 
and, though they seera to have saved a few isolated herds, will fail disastrously if 
generally relied on. The epizootic influence, too, though apparently all-powerful in 
localities where the poison has already penetrated, fails to produce the disease in the 
neighboring States not previously infected. We can not give too much attention to 
secure the best sanitary conditions of life for the hogs, but if we allow a few of these 
so to engross our attention that our eyes are blinded to the most important of all — 
the prevention of contagion — we shall only spread the poison and increase the de- 
struction of our herds. On the other hand, the highest success must attend such 
measures as will stop the production of the poison and destroy and render innocuous 
what is already in existence. 

Diseased pigs must be removed from the healthy, killed, and buried. A thorough 
disinfection of all buildings, yards, and manure must be made. Chloride of lime or 
zinc, sulphate of iron, or carbolic acid may be used for all solids, floors, troughs, 
walls, etc., and for drains ; and sulphurous acid or chlorine for the atmosi)here. The 
sulphurous acid may be produced by burning sulphur,.and the chlorine by adding oil 
of vitrei to common salt and a little black oxide of niauganese. The surviving pigs 
must be carefully Avatched for the first signs of illness. Any unusual sluggishness, 
stiffness, or inapjietence, or .any disposition to leave the herd, demands a careful ex- 
amination ; and if there is heat or shivering, and, above all, if the thermometer in- 
troduced into the rectum indicates a temperature above 103^ Fahrenheit, the animal 
should be at once separated from the herd, and destroyed as soon as uuequivocal 
symptoms of the malady are shown. Care should be taken to avoid the possibility of 
contamination by Avater which has passed infected hog-pens or fields. If the malady 
exists within a wide radius, the visits of dealers and others must be absolutely for- 



28 

bidden, and a similar probibitiou sbould attacb as far as possible to quadrupeds aud 
birds, wild and tame. Disinfectants may even be given to the sound animals that 
have been exposed to contagion. A table-spoonful of charcoal, animal or vegetable, 
may be given daily to each pig in its food. Twenty grains of bisulphite of soda, or 
ten drops of carbolic acid, or 10 grains of sulphate of iron may be used instead, and a 
tea-spoonful each of 8ul})hur aud gentian may be added with advantage. When a herd 
has been freed from the disease, a most exhaustive disinfection of the whole premises, 
manure, aud other products is imperative, aud it is usually desirable to change the 
site of the hog-pen and run to obviate any future effects of this most virulent conta- 
gion. Old and rotten wood work should be burned. 

In purchasing pigs, buyers will consult their interests by avoiding markets, and 
going rather to the breeders whose stock is known to be healthy, aud by seeing per- 
sonally to the thorough cleansing and disinfection of loading-banks, cars, boats, etc., 
which they must use iu bringing them home. And after all such iirecautions, newly 
purchased swine should invariably be jdaced in quarantine, at a safe distance from 
other hogs, and kept there for three weeks, with separate atteudants, until they have 
been proved sound. 

As in the case of other fatal contagions, this could doubtless be kept iu check, or 
even completely extinguished, by a uniform system of destruction of the infected, 
and disinfection of their cai'casses aud all v/ith which they have come iu contact. 
Such a proceeding would imply an amount of governmental supervision and pecuni- 
ary outlay that would be profitable in the long run, though the jiast experience of 
the American people have scarcely prepared them to sanction it. 

Ill 1877, a paper written by H. J. Detmers, V. S., giving his obser- 
vations of the disease generally called Log cholera, aud bis conclusions 
as to its nature, was reprinted in the aunual report of the Department 
of Agriculture. Dr. Detmers proposed to call the malady "epizootic 
influenza of swine," aud he divided it into (1) " the catarrhal rheu- 
matic form," (2) " the gastric-rheumatic form," (3) " the cerebro-rheu- 
matic form," and (4) "the lymphatic-rheumatic form." The causes of 
the disease he divided into three classes, and he writes : 

As belonging to the first class I look nj)on everything that will interrupt or disturb 
the perspiration ; in the second class I place all such noxious influences and agencies 
as interfere directlj' with the process of respiration ; finally, in the third class, I put 
all such noxious agencies or injurious influences as tend to aggravate the disease if 
already existing, by aiding in making its character more typhoid, or which produce 
a special predisposition by weakening the constitution of the animal. 

In regard to the contagiousness of the affection he says: 

Still I think the epizootic character of the fearful spreading of the disease can be 
satisfactorily explained without the existence of a contagion. 

The above extracts show the most divergent views among physcians 
and veterinarians as to the cause and nature of the epizootics among 
swine. At the same time'there were equally wide differences of opinion 
among swine-breeders and the contributors to the agricultural press. 
In short, there was the greatest uncertainty and confusion of ideas not 
only as to the characters of the disease or diseases, but as to the most 
elementary principles to be applied for prevention. 

It was just at this period (1878) that Congress provided for the first 
investigation of swine diseases by making an appropiiation of $10,000 
for this purpose. The beginning of this investigation, which has been 



29 

continued with sliort interruptions until the present time, marks a new 
era in our knowledge of swine epizootics and of contagious diseases in 
general. It was just at the time when the biological researches of Pas- 
teur in regard to fermentation were attracting- so much attention, and 
had already inspired Lister to make his discoveries in antiseptic sur- 
gery, and Koch to institute those researches which definitely connected 
the bacillus anthracis with the causation of charbou. The time was 
propitious, therefore, for the institution of a new line of researches, in 
a direction which even then promised much, and which since has prac- 
tically revolutionized the position of medical science as to the nature 
of contagion and the methods most important for its control. 

The writings of Drs. Sutton, Snow, and Law gave a very cdrrect state- 
ment of the symptoms undjwst mortem appearances of the organs usually 
found in the swine epizootics of this country. The^^ covered about all 
the points which can be decided by ordinary field observations, but they 
left many questions still unsolved which it was necessary to determine 
before measures of prevention could be formulated and made successful. 

There were many who believed that these epizootics were due to the 
ravages of more than one disease, and there were also many who held 
that contagion and infection played no part in their extension. As to 
the nature of the agent or agents which caused the outbreaks, or the 
conditions which were required to prevent their destructive ravages, no 
results of value had been obtained, or indeed could be, without a more 
systematic and persistent investigation, with all the instruments, ap- 
paratus, and laboratory facilities which are required to work out the 
obscure problems of pathological science. As with other contagious dis- 
eases of men and animals, the instruments of the post-mortem case had 
been the means by which a certain amount of information had been 
gained, but there were problems which they could not reveal, and for 
these the microscope, the culture apparatus, the biological and chemi- 
cal laboratories were necessary, and without these a reliable solution 
could not be reached. 

For the investigutions of 1878 nine men were appointed for a period 
of two months each, as follows : Dr. II. J. Detmers, Illinois ; Dr. James 
Law, New York ; Dr. D. W. Voyles, Indiana ; Dr. D. E. Salmon, North 
Carolina; Dr. Albert Dunlap, Iowa; Dr. E. F. Dyer, Illinois; Dr. A. 
S. Payne, Virginia ; Dr. J. N. McNutt, Missouri; Dr. C. M. Hiues, Kan- 
sas. The researches were to be made in the field in different sections 
of the country, and various remedies, suggested as applicable to tlie 
treatment of epizootic diseases, were to be tried. The result of this 
investigation may be summed up practically as follows : (1) Swine dis- 
eases were found destructive in the most widely separated districts of 
the country. (2) The symptoms and lesions enumerated were similar to 
those formerly given by Drs. Sutton, Law, and Snow. (3) No evidence 
was discovered to show the existence of more than one disease which 
prevailed as an epizootic. (4) There was a preponderance of opinion 
that the outbreaks were due to contagion and that the disease was com- 



30 

municable. (5) The remedies tested eitber produced no effect or were 
of doubtful vabie for the treatment of affected animals or for guarding 
against tbe contagion. , 

Tbere were two points of more than usual interest raised in the inves- 
tigation. In tbe course of Dr. Law's investigations be made inocula- 
tion experiments witb rabbits, rats, and sbeep, which he thought dem- 
onstrated the communicability of the disease that he investigated. 
Dr. Detmers devoted more of his time to microscopical investigations, 
and asserted that be had discovered a specific micro-organism, which 
he called the Bacillus siiis, and that he had demonstrated its pathogenic 
connection with the disease. 

Both of these conclusions must now be looked ui)ou as premature and 
not supported by the direct and positive evidence which is necessary 
to establish such important points. That Dr. Law produced disease in 
tbe experimental animals which he inoculated is not to be doubted for 
a moment, but that it was the same disease and caused by the same 
microbe which produced the swine eijizootics of the country could only 
be definitely determined after the microbes of the swine diseases had 
been identified and their characters established. Very frequently in 
inoculating with the products of disease taken from dead animals, septic 
disorders are caused in the inoculated animals which are entirely dif- 
ferent in nature from tbe malady which caused the death of the indi- 
vidual inoculated from. To determine, therefore, whether the disease 
induced is identical with the disease which we propose to propagate by 
inoculation it becomes necessary to determine the microbe which causes 
the morbid changes in each case. At that time neither of the microbes 
which we have since identified and studied in swine epizootics in this 
country had been discovered, and consequently the line of evidence 
just indicated was impossible. 

Dr. Detmers's culture experiments were too crude and primitive to be 
of any value, even in the condition in which bacteriological science was 
at that time; and his descriptions of the germ might be applied with 
equal accuracy to many different species of micro-organisms. For this 
reason no attempt will be made in this volume to give the details of 
either the culture or inoculation experiments which he made. While 
failing to obtain the evidence necessary to establish the connection of 
any micro organism with the production of this malady, this and sub- 
sequent reports of Dr. Detmers had some effect in directing the atten- 
tion of investigators in this country to bacteriological researches as a 
promising field in which to search for the hidden mysteries connected 
with this class of diseases.* 

* It is due to justice to state iu this conuectiou tliat, whereas the appointmeuts lim- 
ited the work of those selected for the investigatious of 1878 to a period of two mouths, 
Drs. Detmers aud Law were subsequeutly giveu au opportuuity to coutiuue their iu- 
Ycstigatlons for a much longer period. It is also jiroper to state that several mouths 
hefore the investigatious of 1878 began, Dr. Kleiu, of Loudon, had published investi- 
gatious which he believed established the fact that the swiue epizootics of Great 
Britain were caused by a baoiUu^i. See Quarterly Journal of Microacopici^l Science, 
April, 1878. 



31 

The investigations of tlie Department of Agriculture were continued 
in 1879 by Drs. Law and Detmers ; in 1880 by Drs. Law, Detmers, and 
Salmon, and in 1881-'82 by Drs. Detmers and Salmon. The efforts of 
Dr. Law were largely directed to obtaining a modified virus for prevent- 
ive inoculation, a doubly difficult and discouraging task before the mi- 
crobes of the diseases had been discovered and studied. While his 
results were more or less encouraging, no conclusions of practical value 
as to a method of preventive inoculation were established. 

Dr. Detmers continued his microscopic observations and modified his 
first descriptions of the microbe so far as to speak of it in later reports 
as a micrococcus. The author devoted the greater part of his time during 
these years to an investigation of southern cattle fever and fowl cholera, 
but incidentally investigated a number of outbreaks of swine diseases. 
He found micrococci in the liquids of the affected animals, which he 
cultivated and inoculated into other animals, but his results were not 
sufficiently positive to demonstrate their connection with the disease. 

There was here a period of about four years when the investigations 
of swine diseases gave no very decided advance in our knowledge of 
the subject. The reason for this was that the investigation had been 
carried about as far as was jDossible by the methods then employed. 
To get a better insight into the nature of the epizootics and the pecu- 
liarities of the contagion, it was essential that the pathogenic microbes 
should be discovered and accurately studied. The investigators saw 
this and were working in the proper direction, but at that time bacteri- 
ological science was young and the methods of research had not been 
clearly worked out. Another and equal difficulty was the fact that 
the investigators were working without proper laboratory facilities and 
apparatus for such researches, without assistants, and some of them 
were devoting much of their time to other duties. Under such condi- 
tions it is next to impossible to reach successful results in such a diffi- 
cult field of study. These difficulties were not fully appreciated either 
by the officials of the Department of Agriculture or by the stock-owners 
of the country, for the reason that such investigations were new to them 
and their requirements but imperfectly understood. It was not expected 
that a chemist would go into a sorghum field and discover the propor- 
tion of cane sugar in the sorghum cane without apparatus or laboratory 
facilities, but it was expected that the veterinarian would make much 
more difficult and delicate investigations than these with no other aids 
than an ax, a butcher knife, a scalpel, and a microscoi)e. 

The author saw that jnore facilities must be provided for these in- 
vestigations, and the work systematized and properly divided, or the 
final result would be disappointment and failure. It was through his 
urgent representations that a beginning was made in 1883, by securing 
an unoccupied room under the roof of the Department buikling, which 
was fitted up as a laboratory, and by obtaining i)ermission to rent a 
small place in the suburbs of Washington on which to keep expert* 
mental animals. 



32 

The year 1883, however, was one in which the necessity of investigat- 
ing the prevalence of the hmg plague or pleuropneumonia of cattle 
became too urgent to admit of delay. There were frequent outbreaks 
which it was the duty of the chief of the veterinary division to visit 
and give assistance to the State authorities as to their diagnosis and 
eradication. This precluded any systematic investigations of swine 
diseases. The spring of 1884 brought the extensive outbreaks of ergo- 
tism in Kansas, Missouri, and Illinois, which alarmed the whole coun- 
try, and which demanded instant attention : and these unfortunately 
were followed, in the summer, by the outbreaks of pleuropneumonia in 
Ohio, Illinois, and Kentucky, which required the constant attention of 
the chief veterinarian and prevented scientific researches for several 
months. 

The investigations during the years 1883 and 1884 were, therefore, 
too much interrupted to allow the number of experiments and the thor- 
ough working out of details which was desirable. The time was not 
entirely barren of results, however, in the investigation of swine dis- 
eases. The laboratory was fitted up and suitable microscopic and bac- 
teriological apparatus obtained. Able assistants were selected and 
placed in charge of the different branches of the work. The lines of 
research were marked out and such arrangements made as would per- 
mit of the intelligent prosecution of the work, even in the absence of 
the chief of the bureau. 

This systematization of the investigations, with the employment of a 
proper number of persons to keep the different lines of study advancing 
uniformly, was followed almost immediately by the most important de- 
velopments. In 1885 a motile bacillus was discovered to be the cause 
of hog cholera, and its leading characteristics were accurately de- 
scribed. In 1886 the production of immunity by chemical products was 
demonstrated, the effect of disinfectants on the hog cholera contagion 
was thoroughly studied, and the i)resence of swine plague, a second 
epizootic disease of swine, was discovered. These discoveries solve the 
most important problems connected with swine epizootics and give a 
secure scientific basis from which to work in future. In fact these dis- 
eases are now much better understood than are most of the contagious 
diseases of people, and the measures applicable, in the present condi- 
tion of science, to their prevention are equally as apparent as are those 
which are applied to the plagues of mankind. 

In the sections of this work which follow the details of the investiga- 
tions of hog cholera made since 1884 are given as fully as are consid- 
ered necessary to an understanding of the different phases of the sub- 
ject. The account of the experiments in regard to swine plague are 
reserved for publication in a separate volume, which it is hoped will 
appear within a few months. 



SYMPTOMS AND POST-MORTEM APPEARANCES IN HOG CHOLERA. 



The symptoms are uot entirely characteristic, owing to the many 
forms which the disease may assume. It is moreover quite trouble- 
some to make careful thermometric aud other clinical observations on 
swine, which enhances the difficulty of exactly determining the course 
of the malady. In general we may regard the disease as manifesting 
itself in an acute and a chronic or mild form. 

Of the acute form very little need be said. The animals die very 
suddenly, without having been sick for more than a few hours to a day. 
The chronic disease may last from three weeks to several months. The 
animals grow stupid and dull, they refuse to eat, and are ajit to sepa- 
rate themselves from the rest of the herd. They grow weak, and their 
movements become slightly tottering. A common symi)tom is diar- 
rhea, which may appear very soon after the animal becomes sick and 
last until it dies. In protracted cases the liver may become affected 
secondarily through the impaired condition of the large intestine. 

The following symptoms, as noted for three or four years by Dr. Kil- 
borue at the experiment station of the Bureau, will show how little 
there is upon which we can depend for a diagnosis during life. 

The temperature of healthy pigs ranges between 101° and 104J° F. 
With sick animals it may rise from 1° to 0° above the temperature ob- 
served in health. Frequently this elevation is absent. During an out- 
break elevation of temperature may be considered diagnostic, but ab- 
sence of such elevation proves nothing, since an animal may die with- 
out having shown any rise of temperature during the disease. There 
is rarely any cold or shivering stage. The sick animals are dumpish, 
spiritless, and lie quietly in a corner or huddle together, hiding the 
head under the litter. They refuse to move even when disturbed, and 
are more or less oblivious to surroundings. 

There is more or less loss of appetite. They usually continue to eat 
a little, however, and often the appetite is scarcely impaired during the 
whole course of the disease. Acute cases may be seen feeding before 
they are found dead an hour or so later. In most cases the stomach is 
well filled after death. 

The bowels may be costive at the outset or continue apparently 
normal for some time, or they soon become costive, and remain so in 
some cases throughout the disease. In the later stages diarrhea of a 
15612 H c 3 33 



34 

liquid, fetid character appears in many cases. The color of the dis- 
charges depends hirgely upon the feed. In slop or garbage fed pigs 
they are usually of a dirty black color. In those fed with grain they 
are light yellowish. The diarrhea persists until death. Vomiting is 
absent. 

Eespiration is only occasionally quickened and labored in the later 
stages. The pulse is more rapid than in health, but its determination 
unsatisfiictory, owing to the struggle of the animals when held. Cough 
is infrequent, and then only heard when the animals are aroused, as a 
single eftbrt or in paroxysms. 

The skin is frequentl}' found reddened on the nose, abdomen, inside 
of limbs, the ears, and over the i)ubic region. The redness is diffuse, 
varying from a slight blush to a deep bluish red or purple. It increases 
as death approaches, and is usually found at the autopsy. A skin 
eruption appears occasionally, which is followed by crusts or scabs of 
varying size. Eeddening of the skin is a symj^ton common to the other 
swine diseases — rouget and swine plague. 

The eyes are apt to be watery. This is frequently the first outward 
sign. Later the discharge becomes thick, yellowish, often gumming 
the lids together. 

Towards the end of the disease the animals have a gaunt appearance, 
with arched back and staring coat. Emaciation is very rajiid. The 
weakness manifests itself in a staggering, uncertain gait, as if the 
animal were about to fall. Death ensues quietly. Rarely convulsive 
kicking is observed. The mortality is very high, usually from 80 to 90 
per cent, of those attacked die. 

These symptoms vary in intensity, and onl}- a certain number are seen 
in one animal at the same time. In very chronic cases only the autopsy 
enabled us to make a diagnosis. 

LESIONS PRODUCED BY HOG CHOLERA. — POST MORTEM APPEAR- 
ANCES. 

(See Plates I-VIII iuclnsive.) 

a. The acute type. — This might with equal propriety be called the 
hemorrhagic type, inasmuch as the chief and perhaps the only changes 
are hemorrhagic in character, and these lesions are seen most clearly 
when an animal is examined immediately after death. The spleen is 
variably enlarged, soft, gorged with blood. Sometimes it is twice as 
long as the normal spleen (the other dimensions being proportionately 
increased), and it may extend across the median line to the right side. 
Next to the spleen the lymphatic glands and serous membranes are 
most severely involved. The cortex shows, on section, as a hemor- 
rhagic line or band, according to the amount of extra vasated blood, or 
the entire gland may be infiltrated with it. Among the glands most 
commonly hemorrhagic are those of the meso-colon (large intestine), 



35 

those at the root of tlie lungs (broncliial), and on the posterior thoracic 
aorta. Besides these, the retro-peritoneal and gastric ghmds (lesser 
omentum) may be involved. IVLost rarely the mesentric glands show 
extravasations to a slight extent. Hemorrhages are also quite frequent 
beneath the serous surfaces of abdomen and thorax. They are most 
abundant under the serosa of the large and small intestines as petec- 
chisB and larger patches. They are occasionally found under the i)eri- 
toneum near the kidneys, the diaphragm, the costal pleura as extrava- 
sations nearly an inch across. 

The lungs, in a small percentage of cases, show subpleural ecchy- 
moses in large numbers, and on section small hemorrhagic foci are ob- 
served throughout the lung tissue. In a few cases severe hemorrhages, 
involving one or more lobes, have been observed. The kidneys are oc- 
casionally the seat of extensive hemorrhagic changes. The glomeruli 
appear as blood red i)oints ; larger extravasations occur in the medul- 
lary substance, and blood may collect around the apices of the papil- 
Icie. The subcutaneous tissue over the ventral surface of the body may 
be dotted with petecchiie and occasionally collections of blood (ba^mato- 
mata) are found in the superficial muscular tissue. The brain and 
spinal cord have not been examined for want of time. In one case, 
however, in which they were laid bare, petecchia; were seen on the cere- 
bellum. 

The digestive tract usually is the seat of extensive lesions. The fun- 
dus of the stomach is as a rule deeply reddened ; there may be more 
or less hemorrhage on the surface, giving rise to patches or larger sheets 
of blood clots. The small intestine in some cases has submucous eccby- 
moses throughout its entire length. In the large intestine the ecchy- 
moses may be so numerous as to give the membrane a dark red ap- 
pearance. The food is now and then found incased in sheets of blood 
clot due to hemorrhage on the surface. 

b. The chronic form is perhaps the most common, at least iu those 
epizootics which we have studied. The acute hemorrhagic cases usually 
die in the beginning of an outbreak and are apt to be overlooked. Fol- 
lowing these are the more protracted, milder cases. In these animals 
the disease is apt to be limited iu its severe manifestations to the 
large intestine. The other organs, however, are not exempt from degen- 
erative changes, owing in part to the impairment of the functions of the 
large intestine, consequent fermentations and the absorption of poisons 
thereby produced, in part to the preseuce of tiie specific bacteria iu the 
spleen and presumably in other organs where they exercise their poison- 
ous activity. 

The lesions of the large intestines are necrotic and ulcerative iu char- 
acter. The ulcers uuiy be isolated and appear as circular, slightly-pro- 
jecting masses stained yellowish or blackish or both iu alternate riugs. 
Or they may be slightly depressed and somewhat ragged in outline, 



36 

When the superficial slougii is scraped away many ulcers show a gray- 
ish or white bottom. A vertical section reveals a rather firm neoplastic 
growth, extending usually to the inner muscular coat. When sections of 
such an ulcer are stained with aniline dyes and examined under the micro- 
scope w^e notice the submucous tissue very much thickened, infiltrated 
with round cells, and containing a large number of dilated vessels. 
Eesting upon this thickened submucosa is aline of very deeply-stained 
amorphous matter, and upon this is situated the necrotic mass which 
fails to retain the coloring matter and is penetrated by an immense num- 
ber of bacteria of various kinds. Frequently ova of trichocephalus are 
imbedded in the slough. 

The extent of the submucous infiltration depends upon the age of the 
ulcer. In old ulcers it contains many newly-formed capillaries, and 
evidences of the formation of connective tissue are present. The 
capillaries may extend to the very edge of the border where the slough 
begins. The latter may have been partly shed, leaving a smooth line 
bounding the cicatricial tissue. The submucous infiltration gradually 
disappears as we leave the center of the ulcer, and somewhat outside 
of the ulcer no inflammation of the membrane is observable. Giant 
cells may be seen in some cases in the iutertubular tissue at the edge 
of the ulcer. In very young ulcers it is frequently possible to observe 
the fundi of the tubules intact, while the inner or free half is converted 
into an amorphous mass. The depth to which the infiltration extends 
is not always limited to the submucosa; it may extend into the muscular 
coats and cause inflammatory thickening there and inflammation and 
the formation of new vessels in the subjacent serosa. 

In some cases the necrosis, instead of appearing in circumscribed 
ulcers from one-sixteenth to one-half inch or more across, involves the 
whole surface of the mucosa, giving it the appearance of a so-called 
diphtheritic membrane. In such cases the walls of the intestine are 
very mnch thickened and so friable as to be easily torn with the for- 
ceps in handling. Such necrosis is rare in spontaneous cases, but it 
quite invariably appears in animals which have been fed with pure 
cultures of hog cholera bacilli. 

The distribution of the ulcers varies but slightly. They appear most 
frequently in the ciecum and on the ileo-crecal valve, as well as in the 
npper half of the colon. The lower half is implicated in severe cases 
only, and then less extensively. The rectum is only very rarely ulcer- 
ated. The lower portion of the ileum is ulcerated in a small percentage 
of animals, especially when they have been fed with hog cholera vis- 
cera or cultures. The stomach is occasionally the seat of slight ulcera- 
tion. The lymphatic glands of the affected intestine are usually much 
enlarged, pale, tough, whitish on section. The spleen is rarely enlarged; 
the liver shows degenerative changes (softening of the parenchyma, 
increase of connective tissue). Heart and lungs are usually normal. 
The lobular pneumonia frequently found in young pigs in the winter 



37 

months must be ascribed priaiarily to exposure rather Ihau to the (li«- 
ease, as will be shown subsequently. 

In some outbreaks the acute and the chronic types of the disease are 
not so clearly distinct as given in the foregoing pages. Frequently re. 
cent hemorrhagic lesions seem to be grafted upon cases presenting ex- 
tensive ulcerations, which certainly are much older than the extravasa- 
tions. It may be that the latter are the result of a secondary invasion 
of the hog cholera virus, either from the ulcers in the intestine or from 
without. 

HISTORY AND AUTOPSY NOTES OF AN OUTBREAK OF HOG CHOLERA, 

There is perhaps no better way to illustrate this disease than by giv- 
ing briefly the history of an outbreak in a single isolated herd. In the 
following pages are recorded the autopsy notes and the bacteriological 
examination of such an out])reak near the city of Washington during 
the months of November and December, 1887. A study of this out- 
break was taken up to ascertain more especially the condition of the 
lungs in hog cholera. As it is the fifth or sixth which has been observed 
during the past three years less attention was paid to careful bacterio- 
logical observations. At the same time this phase was by no means 
neglected, as the notes will show. The history of the outbreak as far 
as could be ascertained was briefly as follows : On October 28, there 
were in all one hundred and nineteen swine, chiefly young pigs, weigh- 
ing from 50 to 100 i)onnds. Most of these had been purchased in the 
city markets. At this same time some twenty boar pigs were castrated. 
Within two weeks these began to die, and soon after the others took 
sick, dying at the rate of three to four a day. Less than three weeks 
after the first deaths only sixty-seven remained out of the one hundred 
and nineteen. At the end of the year only about a dozen were alive out 
of the entire herd. These may have acquired immunity. 

The animals were kept in pens on the top of a hillock sheltered from 
the weather by large boxes. They were swill-fed, and this may account 
for their feeble resistance to the disease. In most of them there was a 
cirrhosis of the liver, with softening of the parenchyma, which was prob- 
ably induced by the feeding. The origin of the epizootic could not be 
traced, as the animals had come from various quarters. The city markets 
had proved themselves in the past the source of disease in several pur- 
chases of pigs for experimental purposes. 

The autopsy and bacteriological notes will be given in the order in 
which the animals were examined, any general remarks being reserved 
for the end. The rapidity with which the animals succambed to the 
disease made any very thorough examination quite impossible, since it 
seemed more desirable to utilize all the material by examining those 
organs most always diseased in hog cholera. Most attention was paid 
to the lungs and the digestive tract, while the lungs and the spleen 



38 

were the only orgaus examined bacteriologically. These notes will 
serve to supplement the autopsy notes in the reports for 1885 aud 188G. 

In making cultures from the spleen the following method was usually 
adopted. At tbe autopsy the abdomen was carefully laid open by first 
removing tbe skin and then cutting through the abdominal muscles 
with flamed instruments. The flaps laid back, brought into view the 
spleen not touched as yet by anj- instrument. It was then drawn out 
with flamed forceps, severed from its attachments with flamed scissors 
and placed in a large bottle plugged with cotton wool which had been 
previously subjected to a temperature of 1500-100° C. for two hours. 
In this way it was taken to the laboratory and either immediately ex- 
amined or kept in the refrigerator below SS^* F. over night. In making- 
cultures the s])leen was placed on a sterile glass support and the surface 
thoroughly charred with a red-hot platinum spatula. This was always 
done, although seemingly unnecessary when we consider the momentary 
exposure to the air in transferring the S[)leen from the abdomen to the 
sterile bottle. It may, however, destroy any bacteria which have 
entered the peritoneal cavity through ulcers. Through this charred 
area an incision or rent was made and a platinum wire introduced, and 
then a tube of gelatine or beef infusion inoculated with it. When roll 
cultures were made a minute bit of spleen pulp was torn away from be- 
neath the charred portion and stirred about in the liquefied gelatine. 
From this usually a second tube was prepared. Experience of past 
years had shown that frequently this is not sufficient to insure the fer- 
tility of the cultures. In chronic cases with tbe spleen but moderately 
enlarged, hog cholera bacteria are found in very small numbers. lu 
such cases bits of spleen are cut out trom the charred area with flamed 
scissors and transferred to tubes of gelatine or beef infusion with or 
without peptone. Such cultures rarely fail. It might be supposed 
that the chances of accidental contamination are very great in this pro- 
cess. But a long experience with spleens of healthy animals and with 
organs in tbe study of other diseases has demonstrated the entire safety 
of this procedure, Salmon culture tubes with bits of organs in the bottom 
covered by nutrient liquids have remained sterile for months in the 
laboratory. At present the Esmarch tube or roll culture is indispens- 
able in such cases. 

In nearly all the cases examined both liquid and gelatine cultures 
were made. The former permit a diagnosis on tbe following day, while 
the latter require at least two days, usually three or four, before a re- 
liable diagnosis can be made. The cultures were always examined un- 
stained in a hanging drop, as the bacteria in this way are not deprived 
of their power of motility, which is one of the im])ortant diagnostic 
characters. Staining cultures was also resorted to, but it adds little in- 
formation to that gained by a careful examination of the hanging drop. 
When gelatine cultures were examined the bacteria were always mixed 
with some sterile beef infusion to bring out their motility. 

In a number of cases rabbits were inoculated directly Irom lung tis- 
sue. A small bit, about one half centimeter cube, was torn up with 
flamed forceps in a flamed watch glass containing some sterile beef in- 
fusion, and the turbid fluid injected beneath the skin of the thigh. The 
syringe used was an ordinary hypodermic syringe carefully disinfected 
by 5 per cent, carbolic acid above and below the piston for one-half 
hour both after and before use, and each time thoroughly rinsed in boil- 
ing water. As hog cholera bacteria are destroyed by a 1 per cent, so- 
lution of carbolic acid in less than ten minutes, and by a momentary 



39 

contact with water near the boiliug poiut the disinfection was certainly 
all that could be desired. This method was rejjarded as less open to 
criticism than the iusertion of bits of tissue under the skin. We still 
stand in need of a syriuge which can be disinfected without much trouble, 
as the above method is extremely tedious. The syringes devised by 
Koch are both unsatisfactory. The joints formed by the glass barrel 
and the metal cap in the syringe in which the propelHng force is air 
were found to leak in five out of six samples. From the fluid injected 
into rabbits either i)late or roll cultures were made in order to get 
an idea of the approximate number and the kind of organisms present. 
In every case the portion of lung tissue from which the inoculations 
were made was transferred to sterilized bottles and protected from ac- 
cidental contamination as carefully as possible. Unless otherwise indi- 
cated, the methods just given were employed throughout the investiga- 
tion. 

November IC. — Pig No. 1, just died aud brought to experimental sta- 
tion. No skin lesions; heart and lungs normal with exception of a few 
colhipsed lobules in principal lobe of one lung.* In abdomen omentum 
injected so as to appear bright red. Spleen enlarged, soft, dark. Some 
lymphatics have the cortex hemorrhagic. Stomach and small intes- 
tines normal. In ctecum near valve several large superficial yellowish 
ulcers and a number of smaller ones, an eighth of an inch in diameter. 
Two bits of spleen were cut out and dropped into a tube of gelatine, 
and one of beef infusion. The gelatine culture remains sterile. The 
liquid culture contains the motile hog cholera bacteria and a large bu- 
tyric bacillus growing only in the bottom of the liquid. 

No. 2 died last night. Buzzards have eaten into the thorax aud 
i;)enetrated the coats of the stomach. Only the small ventral lobe 
of right lung diseased. Bright red, mottled with pale yellow dots. 
(See Plate IX, fig. 2.) The smallest bronchi occluded by cylindrical 
plugs. Alveoli likewise occluded. The pings consist chiefl}'^ of cells 
and are so dry and firm that they may be removed as small ramifications 
or branchings when the lung tissue is torn away. Bronchial glands 
enlarged, hemorrhagic. Spleen enormously enlarged, liver in advanced 
stage of cirrhosis. Glands at portal fissure chronically enlarged. In 
caecum four superficial ulcers one-half inch across, slough stained yel- 
low. In upper colon four similar to these and a large number of small 
ones about one-eighth inch across with yellowish slough. 

A moderate number of bacteria found in cover-glass preparations of 
spleen. A gelatine tube culture contained, after three days about, sev- 
enty-live to one hundred colonies of the motile hog cholera bacteria in 

* Iq order to uuderstaud the description of the Inng lesions, the following brief 
outline of the anatomy of the lung and of the terms nsed may be of service: 

The right lung is made up of four lobes ; the left has oniy'three. (In text-books 
on anatomy the left lung is considered as being made up of only two.) 

In both there is a large principal lobe resting upon the diapbragm and against the 
adjacent thoracic wall. This lobe forms the major part of each Inug. The remainder, 
occupying the anterior (or cephalic) portion of the cavity, is made up of two small 
lobes, one extending veutrally (or downward in the standing position of the animal) 
aud in the expanded state covering tiie heart 1 iteraljy, the other extending towards 
the head and overlapping the base of the heart. These small lobes may be denomi- 
nated the ventral and cejjhalic lobes, r(\siieclively. The right cephalic lobe is longer 
and more distinct from the ventral lobe than the corresponding left cephalic. Wedged 
in between the two principal lobes and resting on the dia|)hragm is a small lobe, 
pyramidal, belonging to the right lung (azygos lobe). This lobe rests on the left 
against the mediastinal membrane, and ou the right it is separated from the right 
principal lobe by a fold of the pleura passing from the ventral abdominal wall to in- 
close the inferior vena cava. This small lobe is almost completely shut otf, therefore, 
from the other lobes by folds of the pleura. 



40 

each ueedle track. A liquid culture inoculated simply with the platinum 
wire thrust into the spleen pulp contained hog cholera bacteria only. 
A rabbit was inoculated from lung tissue as above described ; about one- 
fourth of a cubic centimeter of the suspension injected. Dead on the 
seventh day. Slight fibrinous exudate on coils of intestines. Spleen 
very large, soft, dark. Beginning coagulation-necrosis in liver. Bac- 
teria very numerous in spleen; both gelatine and liquid cultures contain 
only the motile hog cholera bacteria. The plate from lung tissue with 
which rabbit was inoculated contains a very large number of identical 
colonies, made up of motile hog cholera bacteria. 

November 17. — No. 3, male, died yesterday. Buzzards have consumed 
pectoral muscles and pierced into thorax and abdomen. Ecchymoses on 
costal pleura and entire epicardium, a few under pulmonary pleura. Left 
lung hypostatic, slight amount of whitish foam in trachea. Lung tissue 
otherwise entirely normal, neither hepatization nor collapse anywhere 
to be seen. Bronchial glands and those along posterior aorta with hem- 
orrhagic cortex. Ecchymoses in the subcutaneous fatty tissue over en- 
tire ventral aspect of body, about one-eighth inch across, beneath peri- 
toneum of abdominal muscles and of the entire length of small intes- 
tine, from size of pin's head to one-eighth inch. Congestion in patches 
in large intestine, no ulceration. Stomach and intestines contain a yel- 
low liquid resembling the yolk of eggs. Spleen but slightly enlarged. 
Ecchymoses under serosa of liver. Cirrhosis moderate. A bit of spleen 
tissue dropped -into a tube of beef infusion gave rise to a culture of hog 
cholera bacteria. In each needle track of a gelatine culture countless 
colonies of the motile bacteria appear. 

November 18. — No. 4, medium sized male, died this morning. Super- 
ficial inguinal glands enlarged, cortex slightly hemorrhagic. Some 
fibrils on coils of intestine. Petecchi.e under serosa of small intestine ; 
extensive hemorrhage between mucous and muscular coat of stomach 
along fundus, forming a clot about one-half inch thick. Spleen very 
large, friable, blackish, extends beyond median line into right side. 
Petecchiie on liver, which- is considerably cirrhosed ; mucosa of stomach 
along fundus blackish : closely set petecchi;e under mucosa of small in- 
testine; contents liquid, bloodstained. A dark hemorrhagic patch 
near valve in large intestine. Colon studded with petecchia?, no ulcera- 
tion. Small number of petecchioe on surface and throughout cortex of 
kidneys. No bacteria seen on a cover- glass preparation of spleen tissue. 
Beef infusion inoculated with a wire thrust into spleen remains sterile. 
A bit of spleen dropped into a tube of gelatine gives rise to about a dozen 
colonies of hog cholera bacteria. 

November 18. — No. 5, male, 75 pounds, three to four mouths old, died 
last night. Inguinal glands enlarged, pale. Left cephalic, ventral, 
and about one-third of principal, right cephalic and ventral lobes of 
lungs solidified, bright red, mottled with minute yellowish dots, i. e., 
same as No. 2. Costal pleura covered with a very thin whitish exudate. 
Solidified portion of principal lobe adherent. On epicardium a very 
delicate papery deposit. Spleen much congested. Inflammatory ad- 
hesion of liver to diaphragm. Mesenteric glands nearly as large as 
hen's eggs, mottled, pale red. About twelve ulcers one-quarter to one- 
half inch across in lower ileum; base depressed and covered with a thin 
yellow layer; outline irregular; not connected with Peyei's patches. 
Valve thickened and ulcerated. Several ulcers in c;iecum ; a large 
projecting slough attached to one of them. A gelatine and a liquid cult- 
ure from the spleen contain hog cholera bacteria only. A liquid culture 
from the pleura remains sterile. 



41 

A rabbit inoculated from thebepatized lung tissue died on the eighth 
day. Slight fibrinous exudate on intestines, diffuse coagulation necrosis 
in liver, spleen much congested. Immense number of hog c}iolera bac- 
teria in spleen and liver. Cultures pure. A ])late made from the same 
bit of (pig's) lung tissue contains about fifty colonies resembling hog 
cholera. 

Ko. 6, large black male, died last night. Extensive sero-fibrinous 
infiltration of subcutis from axilla to pnbis and over right thigh. The 
subcutis has a gelatinous aspect. Spleen much congested. Lungs nor- 
mal. In cover-glass preparations from spleen large bacilli, with ends 
square. Cultures in gelatine and beef infusion remain sterile. Animal 
l^robably died of malignant oedema. 

Noi-emher 21. — Xo. 7, medium sized male, died yesterday. Tempera- 
ture of air varying from 20° to 50° F. Omentum deeply reddened. 
Spleen enlarged, soft; small hemorrhages under capsule one-eighth 
inch across. Liver imparts a sensation of grittiness when cut. Cortex 
of kidneys dotted with hemorrhagic points. The patch of mucous 
crypts about valve in caecum dark, pigmented; no ulceration. Mucosa 
of stomach hemorrhagic in fundus. Thorax half full of blood-stained 
serum and some fibrin stretching from lung surface to walls ; small 
quantity of fibrin in pericardial cavity. Lung tissue infiltrated with 
blood (pulmonary hemorrhage). Two ventral lobes collapsed; subpleu- 
ral hemorrhagic patches. A cover-glass preparation from spleen con- 
tains numerous hog cholera bacteria. In each needle track of a gela- 
tine culture, countless colonies. A liquid culture from a bit of spleen 
tissue contains hog cholera bacteria only. 

No. 8, small female, died yesterday. Patches of skin on ventral as- 
pect of limbs and groin reddened. Minute petecchiai under serosa of 
ventral abdominal walls. Spleen very large, congested. Some delicate 
fibrils stretched over coils of intestine. Liver cirrhosed. Crlands of 
mesentery and mesocolon enlarged; cortex hemorrhagic. Fundus of 
stomach moderately congested. In caecum are black pigment spots 
resembling former hemorrhage, chiefly on the summit of folds. In 
upper colon ulcers about three to a square inch, each one-fourth inch 
in diameter, and covered by a convex, iirojecting yellowish slough. 
Ulcers found down to rectum. Small quantity of clear serum and a 
few fibrils in pleural cavities and pericardium. Left ventral and tip of 
right cephalic lobe collapsed. A gelatine and a liquid culture made 
from a bit of spleen tissue contain hog cholera bacteria and a butyric 
bacillus which slowly liquefies the gelatine. 

No. 9, small male. Diffuse reddening of ventral aspect of body es- 
pecially marked on limbs. Spleen, lymphatics, and kidneys normal. A 
small abscess in pelvis attached to bladder, probably caused by castra- 
tion. Venous congestion of vessels of mesocolon. The transverse 
folds of mucosa of colon covered by very thin yellowish patches of ne- 
crosis. Feces hard, distending the large intestine. Cephalic and ven- 
tral lobes of left lung solid, plainly mottled. The bronchioles and 
alveoli filled with consistent plugs of cellular exudate. Remainder of 
lungs normal. Owing to small size of spleen, two liquid cultures were 
made, each with a bit of spleen tissue. In both, hog cholera bacteria 
alone appeared. A rabbit inoculated with hepatized lung tissue re- 
mains well for weeks after. A plate culture therefrom is liquefied in 
two days. 

No. 10, small castrated male, died yesterday. Has been sick for some- 
time according to overseer of farm. Spleen not enlarged. Inflammatory 
changes in pelvis due to castration. Stomach slightly reddened and 



42 

bile stained. One large ulcer on ileo ciecal valve one-lialf inch across, 
black, with yellowish margin. A few very superficial ulcers in caicum. 
Lungs normal, lelt somewhat hypostatic. Two cultures made with bits 
of spleen contain both hog cholera bacteria and butyric bacilli. 

No. 11, dying, killed by being bled from brachial vessels. Lungs 
normal. Spleen small. Liver slightly cirrhosed. Two ulceres in ciecum; 
slight superficial necrosis in colon. A liquid culture made from a bit of 
spleen contains hog cholera bacteria on following day. 

November 23. — No. 12, small white male, died yesterday. Median 
line of ventral aspect of body much reddened, limbs slightly so; ex- 
travasation under skin and into muscular tissue over sternum. Much 
blood-stained serum in peritoneal cavity; spleen very large, dark. 
In kidneys, cortex and base of pyramids deeply reddened. In cajcuu), 
slight traces of superficial necrosis. Anterior and cei)lialic lobes of 
both lungs collapsed. Bloodstained serum in pericardium. Numer- 
ous hog cholera bacteria on cover-glass preparations of spleen pulp. 
In a gelatine culture from the spleen countless colonies appear in each 
needle track. A liquid culture made with platinum wire contains hog 
cholera bacteria on following day. A rabbit inoculated from the col- 
lapsed lung tissue died on the tenth day. Spleen engorged ; numerous 
foci of coagulation necrosis in liver, involving each one or more acini; 
extensive necrosis along border of left lobe. Ecchymosis of pyloric 
valve and duodenum; hemorrhagic foci in lungs, about fifteen in each 
lung, one eighth inch to three-sixteenths inch in diameter. Examina- 
tion of the spleen shows numerous hog-cholera bacteria. A gelatine 
culture contains countless colonies in each nee<lle traci\. 

Number 13, small female, died yesterday. Skin on ventral aspect of 
limbs and over pubis reddened. Spleen greatly enlarged, congested. 
Lungs normal. A few lobules in ventral and right cephalic lobe col- 
lapsed. Liver slightly cirrhosed. Stomach distended with food. Large 
patch of mucosa in fundus reddened. Crecum and colon contain numer- 
ous ragged depressed ulcerations. Valve entirely encircled b\' ulceration. 
Contents of intestine liquid, yellow. A gelatine and a liquid culture 
inoculated with a platinum wire thrust into spleen remain sterile. No 
bacteria seen in cover-glass preparations. 

No. 14, small female, weight about 50 pounds. Considerable redden- 
ing of the skin over ventral aspect of body and limbs; especially marked 
along median line. Superficial inguinals enlarged, of a mottled pale 
and deep red on section. Spleen very large, 12 inches long, 2 inches 
broad, and five-eighths to three-fourths inch thick at hilus ; gorged 
with blood, friable. A small number of punctiform hemorrhages in 
cortical portion of kidneys. Glands of mesentery and of colon en 
larged and congested. Deep reddening of several square inches of 
mucosa in fundus of stomach. Large intestine contains a semi-liquid 
mass, chiefly earth. Four large ulcers in ca^'cum, one of them at least 
1 inch across, covered by a yellowish slough; the pi ritoneum covering 
it is thickened and inflamed. In upper colon there is considerable ne- 
crosis, involving the epithelium in patches. Lungs normal, excepting 
the right ventral lobe, which is solid. Bronchi and air cells of this lobe 
completely occluded by plugs as with No. 2; surface bright red, mottled 
with yellowisli points — the idtimate air cells filled with the cellular ex- 
udate. Subi)leural ecchymoses over both lungs. From the spleen a 
liquid and a gelatine culture contained only hog chok^ra bacteria. They 
were very numerous in cover-glass preparations from this organ. 

A rabbit, inoculated from the consolidated lung tissue died on the 
seventh di^y. At the point of inoculation a pasty mass extends to ab- 



43 

domeu, only subcutis involved. Spleen engorged. Single acini and 
groups in the liver are completely necrosed, yellowish white. In both 
organs, hog-cholera bacteria. Cultures from spleen pure. 

November 25. — Xo. 15, black and white male, died yesterday morn- 
ing, lledness of skin of alxlonien, throat, and limbs. Su[)erticial in- 
guinals hemorrhagic. Si)leen very large, gorged with blood. Lungs 
normal, excepting a few lobules at the caudal border of princii)al lobes, 
which are red, collapsed, and contain lung worms. Pericardium con- 
tains dee])-colored serum and coagula; left auricle dotted with petecchiie. 
Bronchial lymphatics hemorrhagic. Liver slightly clrrhosed. Cyst in 
right kidney one-half inch in diameter. Fundus of stomach intensely 
congested, similarly the caicum and colon ; no ulcers. Lymphatics of 
nieso colon hemorrliagic. A beef-infusion culture from a bit of spleen 
contains the motile hog-cholera bacteria only. A gelatine culture be- 
came liquefied by the heat of the laboratory ; no bacteria seen on a 
cover-glass preparation of spleen. 

No. 10, black and white female, died last night. Skin and spleen as 
in previous case. The small ventral lobe of both lungs collapsed, lungs 
otherwise normal. Liver in advanced stage of sclerosis ; stasis of por- 
tal circulation. Lymphatics of abdomen as in No. 15. Fundus of stom- 
ach slightly reddened; one ulcer three-fourths inch across. Extensive 
necrosis of mucous membrane in colon and rectum, slight in cjccum ; 
wherever the membrane is free from a slough it is deeply congested. 
Numerous hog-cholera bacteriaand some large (butyric) bacilli in spleen, 
A beef infusion and a gelatine culture contain them. From a bit of 
collapsed lung tissue a plate culture is made and a rabbit inoculated. 
The plate contains in two days about six to seven liquefying and a 
large number of non liquefying colonies, the latter made up of motile 
hog-cholera bacteria; the rabbit died on the seventh day. Spleen very 
large, friable ; contains large numbers of hog cholera bacteria. On 
left lobe of liver an area of necrosis one-fourth inch by three-fourths and 
one-sixteenth inch deep. On the right lobe only three or four acini 
necrosed. Pylorus and duodenum covered with hemorrhagic dots and 
patches. Culture from spleen pure. 

November 2G. — No. 17, female of medium size; died suddenly this 
morning without previous illness. Subcutaneous fat abundant. Spleen 
moderately congested. Petecchiai in cortical portion of kidneys. Fundus 
of stomach slightly reddened. In lower ileum patches of congestion. 
Scattered petecchiai in mucosa of large intestine; contents normal. 
Glands of mesentery and mesocolon with cortex hemorrhagic. Large 
quantity of bloodstained serum in thorax. Fibrinous deposit on pleura; 
lungs partly expanded ; cephalic half of right lung solid, blackish; air- 
tubes and alveoli filled with extravasated blood. Interlobular tissue 
distended with blood-stained serum (pulmonary hemorrhage). Left lung 
jn the same condition. Trachea full of reddish foam. Blood and fibrin- 
ous coagula in pericardial cavity. Beef infusion, into which a bit of 
spleen was placed, remains sterile; also a tube of gelatine inoculated 
from the spleen with platinum needle. In a cover-glass preparation of 
the spleen large (butyric?) bacilli. 

No. 18, small female, died last night. Buzzards have consumed thigh 
muscles. Diffuse reddening along median line of abdomen. Hemor- 
rhagic spots one-eighth to one-fourth inch across, subepidermal, chiefly 
on ventral aspect of limbs; subcutaneous and subperitoneal ecchymoses. 
All abdominal lymphatics with cortex infiltrated with blood. Serosa 
of large intestines as if sprinkled with fresh blood; several subserous 
hemorrhagic spots one-half inch across on diaphragm, along inferior 



44 

vena cava, common bile duct, and gallbladder; also, under mucosa of 
the whole length of small intestine, throughout cortical portion and be- 
tween pelvis and medullary portion of kidneys. Fundus of stomach 
one mass of petecchiiB and larger extravasations. One ulcer in caecum, 
old, with indurated base. Valve aiul the i)atch of mucous crypts at its 
base ulcerated ; depth of ulcer indurated, con.-isting of a tough, pale 
tissue. Small old ulcers in upper colon. Lungs dotted with small hemor- 
rhages, chiefly subpleiiral. Three or four hemorrhagic patches under 
costal pleura of each side. Lung tissue normal, excepting the base of 
right ventral and the tip of left ventral lobe, which are collapsed. Hemor- 
rhages under epicardium over entire heart; left auricle one mass of ec- 
chymoses. Coagula of fibrin in auriculo-ventricular groove. 

Through an oversight the cultures from this animal and the one fol- 
lowing were both numbered the same, so that it was impossible to 
identify them. A liquid culture from each was made by adding a bit of 
spleen tissue. A gelatine culture from each was made shnply with 
platinum wire. Oue tube of infusion contains hog cholera and butyric 
bacteria; one tube of gelatine contains immense numbers of hog-cholera 
colonies. The other two tubes remain sterile. A rabbit inoculated 
from the collapsed lung tissue remained well for a month after. A plate 
culture from the same contained about six colonies, evidently of hog- 
cholera bacteria. 

No. 19, small male, died last night. Diffuse reddening on abdomen 
along median line. Superficial inguinals very large, pale, oedematous; 
peritonitis ; feeble adhesion of coils of intestine to ventral wall and of 
lobes of liver to one another. Slight fibrinous deposit on intestines. 
Liver sclerosed. Lymphatics hemorrhagic. Cortex of kidneys dotted 
with extravasations. Mucosa of large intestines of a dark slate color; 
it is dotted with closely-set conical elevations, tough, whitish, about one- 
eighth inch high and one sixth across. When scraped away a depressed 
l^ale pink, sharply-outlined spot remains. Microscopic examination of 
the intestine showed that these elevations correspond to amorphous 
masses, which failed to become colored on applying the ordinary stain- 
ing agents. They covered portions of the mucosa which were either 
wholly or partial)}' necrosed and incapable of being stained. In some 
places the outline of the tubules could still be discerned. On applying 
Weigert's fibrin stain, long meshes of fibrin corresponding in general to 
the outline and position of the destroyed tubules appeared. Valve 
thickened and completely covered by ulceration. Cephalic half of both 
lungs airless, affected with bronchopneumonia ; catarrhal exudate filled 
alveoli and air tubes. Epicardium dotted with hemorrhagic points. 
Slight, feeble, pleural adhesions. 

For cultures from spleen, see JSTo. 18. A rabbit inoculated with lung 
tissue died on the fifth day. Spleen slightly enlarged; contains many 
hog-cholera bacteria. Gelatine culture contains very nianj- colonies of 
the same. 

No. 20, a large female. No skin lesions; a few strings of coagula over 
coils of intestine; spleen small; base of pyramids of kidnej^s much 
reddened; ileum dotted with subperitoneal hemorrhagic points and 
patches ; mucosa not affected ; mesenteric glands with cortex hemor- 
rhagic. Large intestine empty, scattered ulcers one-eighth to one-fourth 
inch across. Liver sclerosed. 

A beef-infusion culture inoculated with a bit of spleen tissue contains 
hog-cholera bacteria and butyric bacilli. A gelatine tube culture con- 
tains a few hog-cholera colonies. 

November 29. — No. 21, small Jersey red, female, died last night. Skin 



45 

deeply reddened along median line of abdomen. Large qnaullty of 
blood-stained sernm in peritoneal cavity. Serosa of ileum and Ibe 
mesentery completely covered with bemorrbagic points and patcbes. 
Lympbatics of abdomen bemorrbagic tbrougbout their substance. Pe- 
tecchiiB in cortex of kidneys. Mucosa in fundus of stomach bemorrbagic. 
Mucosa of lower ileum a confluent layer of necrosed tissue. Numerous 
round ulcers in caecum and coUm ; slough projects slightly. Lungs hypo- 
static, interlobular spaces distended with coagulated blood, most marked 
in dependent lobes. Simple colbipse of both ventral lobes and of tlie 
rigbtprincipal near the root. Ventricles of heart dotted with peteccbiie, 
auricles black, covered with clotted extravasated blood. Hog cholera 
bacteria present in cover-glass preparations irom spleen and in both 
gelatine and liquid cultures. 

No. 22, male, Jersey red, died last night. Glands of abdomen with 
cortex infiltrated ^Yitb blood. Spleen engorged. A few hemorrhagic 
patches in fundus of stomach. In cacura and colon ulcers about three- 
eighths inch across ; very thin, adherent, yellowish slough. About one 
ulcer to 4 square inches of surface. Considerable blood-stained serum 
in pleural cavities, hemorrhage in anterior half of left lung, which is 
solid, blackish on section. Clots and reddish foam in trachea and 
bronchi; hemorrhage seems somewhat older than in No. 21. Pleura 
of right lung roughened and i)arts adherent to chest w^all. Ventral 
lobe solid, bronchioles firmly plugged with dry catarrhal secretion. 
Hog cholera bacteria on cover-glass from si)leen pulp and in a gelatine 
and liquid culture made therefrom ; only five to ten colouies in each 
track of the platinum wire. A rabbit was inoculated from a bit of the 
solidified lung tissue and a plate culture made. The latter develops 
numerous colonies of hog cholera bacteria. The rabbit died on the thir- 
teenth day. Numerous bog cholera bacteria in both organs. A gela- 
tine culture from the spleen contains the same organisms. 

No. 23, small black male. Buzzards had removed pectorals of one 
side. Lymphatics congested, not bemorrbagic. Crowded peteccbiann 
subcutis and beneath peritoneum of ventral abdominal wall. Sj)leen 
very large, congested. Four or five small hemorrhages on diaphragm. 
Mucosa of ciecum and upper colon ulcerated in large patches. In 
lower colon the ulcers are small, yellowish, depressed areas embedded 
in a very dark mucosa dotted with numerous punctiform ecchymoses. 
At root of left lung there is some collapse, extending sligbtly.into all 
lobes. Of right lung the ventral and cephalic lobes are collapsed, with 
occasional emphysematous lobules interspersed. Lungs otherwise nor- 
mal. Extensive hemorrhage of ooth auriclesintheform of diffuse patches 
and peteccbitB. A gelatine and a liquid culture from the spleen remain 
sterile. A plate culture made from a bit of collapsed lung tissue con- 
tains a considerable number of colonies, which are made up of bacteriare- 
sembling those of hog cholera, but differing from tliem in their manner of 
growth on gelatine, in beef infusion, and in the absence of motility. A 
rabbit inoculated from the same bit of lung tissue remains well. A 
plate culture from a bit of normal tissue from the same lung contains 
but one colony. 

No. 24 died yesterday; medium-sized female. Spleen very large, 
extends beyond median line. Lungs normal, excepting collapse of a 
small portion of the right ventral lobe. Lymphatic glands in general 
with bemorrbagic cortex. C;ecum and colon very much congested, ul- 
ceration superficial and slight. Entire fundus of stomach of a uniform 
deep wine color. A gelatine and a liquid culture from the spleen con- 
tain onlv motile hog cholera bacteria. In the former the colonies are 



46 

very unmerous. The bacteria are demonstrated in cover-glass prepara- 
tions from spleen pulp. 

No. 25, medium sized black male, died yesterday. Spleen very large. 
Subperitoneal tissue full of i)etecchiie. Lymphatics with hemorrliagic 
cortex. Hemorrbages under serosa of duodenum and common bile duct. 
Valve completely ulcerated. Intestine otherwise normal and feces 
dr3^ Lungs contain a large number of subpleural hemorrhages, tissue 
normal, epicardium hemorrhagic. Kidneys contain a specimen of kid- 
ney-worm [sclerostomapinguicola). A gelatine and a beef infusion culture 
from the spleen became confused with those of another pig (No. 435), to 
be described later on. One set of cultures remained sterile ; the other 
contained hog cholera bacteria. In all probability the sterile cultures 
belonged to this animal. 

December 2. — No. 26, medium-sized female, died last night. Consid- 
erable redness of skin over the ventral aspect of limbs and along me- 
dian line of abdomen. Spleen very large, blackish. Several strong 
fibrous adhesions betweeen costal and pulmonary pleura. Lung tissue 
normal. Left kidney contains a small cyst. Large number of round 
depressed ulcers stained yellow, most numerous in ciecum. One ulcer 
is one-half inch across, the inflammation extending to serosa. Stomach 
very dark, pigmented along fundus. On a cover- glass preparation 
from spleen numerous large bacilli (probably butyric). They did not 
develop in the liquid and gelatine culture, which latter contained only 
hog cholera bactera colonies, very numerous in each needle track. 

No. 27, small black male. Superficial inguinals enlarged, pale, oedem- 
atous. Superficial ulceration and hemorrliagic changes in cfficum. 
Lungs normal. Post mortem changes too advanced for cultures. 

No. 28, small female, died last night. Superficial inguinals with 
cortex hemorrhagic. Spleen slightly enlarged. Minute hajmatomata 
on its surface. Slight sclerosis of liver. Left kidney contains six cysts 
one-half inch diameter. Stomach in fundus somewhat congested. In 
large intestine, ulcers one quarter to three-eighths inch diameter, with 
adherent yellowish, projecting slough, most numerous in ctecum. About 
one-third of the ventral lobe of each lung and a few lobules of the right 
principal lobe collapsed. Lungs otherwise normal. In a beef infusion 
culture from the spleen both hog cholera and butyric bacteria were 
present. A gelatine culture contained but two colonies. From a bit of 
collapsed lung tissue a plate culture was made and a rabbit inoculated. 
On the plate about fifteen colonies of hog cholera bacteria appeared. 
The rabbit died on the fifteenth day. Bare indications of necrosis in 
liver. Spleen very large. Both organs contain a moderate number of 
hog cholera bacteria. A roll culture from the spleen is i^ure. 

No. 29, large black male, died about thirty-six hours ago. Tempera- 
ture below freezing point. Skin deeply reddened over entire ventral 
aspect of body. Superficial inguinals enlarged, slightly congested. 
Spleen very large (about 14 inches long), very soft and friable. Slight 
sclerosis of liver and old perihepatitis. Retro-peritoneal glands with 
cortex hemorrhagic. Cyst in right kidney. Slight ecchymoses in fun- 
dus of stomach. Valve and ])atch of mucous glands in ctecum very dark 
with pigment. Slight superficial ulceration in c;ecum and upper colon. 
Lungs and heart normal. Both gelatine and beef infusion cultures con- 
tain hog cholera bacteria. In the former the colonies are very numer- 
ous. 

No. 30, small black male; died thirty-six hours ago. No reddening 
of skin. Superficial inguinals and spleen but slightly enlarged. Peri- 
tonitis, Petecchise under serosa of small and large intestines and blad- 



47 

der. Moderate amount of flbrinous exudate. Valve completely ulcer- 
ated, ulcer deep. One uear valve has caused thickening' of serosa of 
intestinal wall. In ciecum an extensive patch of ulceration ; in colon 
a few ulcers and numerous punctiforn; hemoirlia.ii'es. Kight lung com- 
pletely adherent to costal pleura by means of fibrous tissue. A small 
ventral portion of principal lobe of left lung is airless, pale red, mot- 
tled with yellowish points. Air tubes and vesicular portion occluded 
with dry cylindrical i)lugs. A culture in gelatine fiom the S[)leen de- 
velops numerous colonies in each track of the Avire. A liquid cuUure 
contains the butyric bacillus also. A bit of the solidified lung tissue 
was used for a plate culture and to inoculate a rabbit. The plate de- 
veloi)ed countless colonies of hog cholera bacteria as tested by other 
cultures. The rabbit died on the tenth day. The spleen was enlarged, 
the liver full of centers of advanced necrosis, involving one to three 
acini ; hog cholera bacteria very numerous in both organs. 

December's. — No. 31, small black and white female, died yesterday. 
Well-markedodor of decomposition. No skin discoloration. Spleen but 
slightly enlarged. Lymi)hatics in general with hemorrhagic coa^tex. 
Liver in state of advanced s^jlerosis. Stomach normal. A few large 
old ulcers and a considerable number of small ones throughout cnecum 
and colon. Mucosa itself pigmented with patches of fresh congestion. 
Lungs normal. A liquid culture from tlie spleen contains only butyric 
bacilli. 

No. 32, small black and white female. No skin discoloration. Lym- 
phatics, including inguinal, bronchial, and peritoneal with more or less 
hemorrhagic cortex. Spleen engorged. Liver sclerosed. Kidneys with 
numerous petecchiai throughout cortical portion. Stomach pale. Sev- 
eral large old ulcers in upper colon. Ciecum and colon pigmented. 
Lungs normal with exception of a few colla]>sed lobules in ventral lobes. 
Both a gelatine and a beef infusion culture contain hog cholera bacte- 
ria. Colonies very few\ 

No. 33, large black and white male; said to have died last night. 
Advanced j;o,s'^ mortem changes. No examination made, excepting to 
see the condition of lungs, which were healthy. 

No. 34, medium-sized w^hite, died last night. Considerable reddening 
over ventral aspect of body. Inguinals reddened on section. Small 
quantity of dark-colored serum and numerous yellowish iiaky coagula 
attached to abdominal organs. Spleen very large, dark, friable. Liver 
cirrhosed. Kidneys with cortical portion thickly dotted with petecchiie, 
hemorrhage into pelvis. Lymphatics in abdomen with cortex more or 
less hemorrhagic. Extensive and deep ulceration in large intestines ; 
in caecum and upper colon as large patches, in lower colon as small 
ulcers. The mucosa which is not destroyed is deeply congested. 
Stomach along fundus deeply reddened. Extensive fibrous adhesions 
of left lung to walls of thorax. Collapse involves ventral, cephalic, and 
portions of principal lobe of right lung, and small i)ortion of principal 
and ventral lobe of left lung. Extensive muco purulent secretion in 
trachea, bronchi, and subdivisions throughout both lungs. Bronchial 
glands with cortex hemorrhagic. A beef infusion culture from the 
spleen contains hog cholera and butyric bacteria. In the gelatine cult- 
ure each track of the wire contains countless colonies of what are shown 
under the microscope to be motile hog cholera bacteria. From a bit of 
collapsed lung tissue a plate culture was made and a rabbit inoculated. 
The plate develops countless non-liquefying colonies. The rabbit died 
on the eighth day. Spleen enlarged. Liver infested with coccidia. A 



48 

sliglit amoimt of coagulation-necrosis. Hog cliolera bacteria in both 
organs and in cultures from the spleen (both gelatine and liquid), 

December 5. — No. 35, small black and white female, died yesterday. 
Eeduess of skin over abdomen and inside of limbs. Spleen enlarged, 
slightly congested. Lymphatics with cortex infiltrated with blood. 
Large quantity of blood-stained serum in abdomen. Liver sclerosed. 
A few scattered petecchiie in cortical portion of kidneys. Mucosa of 
colon pigmented; a few small ulcers present. Lungs normal, with ex- 
ception of a few collapsed lobules in ventral lobe of each lung. Dark- 
colored serum in pericardial cavity. The spleen contains large num- 
bers of butyric bacilli. A liquid culture contains both hog cholera and 
butyric bacilli. A gelatine culture remains sterile. 

No. 36, large black and white female, died yesterday. Lungs normal. 
Spleen very large, dark, friable. Liver sclerosed; lymphatics gener- 
ally with cortex congested or hemorrhagic. Large number of ulcers in 
caecum and colon; mucosa deeply congested. From spleen countless 
colonies of hog cholera bacteria in a gelatine tube culture. In a liquid 
culture the butyric bacilli are also found. 

No. 37, medium Jersey red and the last.of a lot of seven, dead forty- 
eight hours. This animal has been sick for some time ; the spleen 
was very large, gorged with blood. Lymphatics pale. Large number 
of old ulcers, from one sixteenth to 1| inches across in ciecum and colon ; 
mucous membrane generally pale. Of the lungs, both ventral and a 
small portion of cephalic lobes with smaller bronchi and alveoli plugged 
with dry catarrhal products. A liquid culture from the spleen contains 
hog cholera and butyric bacilli. A gelatine culture contains countless 
colonies. The spleen pulp on coverglass preparations shows many. 
From the diseased lung tissue a rabbit was inoculated and a plate cult- 
ure niade. The latter develops a large number of colonies of hog cholera 
bacteria. The rabbit died on the eighth day. Spleen enlarged and 
friable, contains many hog-cholera bacteria. Slight coagulation-necrosis 
in liver, which is infested with coccidia. Cultures from blood and sj)leen 
pure. 

Becemher 7. — No. 38, small white female, died last night. Much ema- 
ciated. Subcutaneous and subperitoneal tissue contains numerous ex- 
travasations. Lymphatics in general with hemorrhagic cortex. Spleen 
moderately congested. Lung tissue normal. Numerous subpleural and 
epicardial hemorrhages. Kidneys with cortical portion dotted with 
numerous punctiform extravasations. Mucosa of small intestine con- 
tains numerous petecchia?. One ulcer, one half inch across, in lower 
ileum. Exteusiveand deep ulceration throughout whole length of large 
intestine. Some of the ulcers over 2 iuches across; surface coal-black; 
the inflammation extending through the intestinal walls to serosa, which 
is dotted with scattered extravasations. A gelatine tube culture from 
S[)leen pulp contains countless colonies in each needle track, consisting, 
as seen under the miscroscope, of motile hog cholera bacteria. A liquid 
culture contains also streptococci and butyric bacilli. 

No. 39, black and white female, 2)ost mortem changes under way. No 
examination made beyond ascertaining that lungs are normal, lym- 
phatics with cortex infiltrated with blood, and spleen enlarged and con- 
gested. 

December 8. — No, 40, small black female, died this morning. Super- 
ficial inguinals enlarged but pale. Moderate quantity of straw-collored 
serum in abdominal cavity. Spleen enlarged, deeply congested. In 
csnecum and upper colon a large number of deep broad ulcers ; in some 
the inflammation extends through intestinal wall to serosa. In lower 



49 

colon, ulcers small and mucosa deeply congested. Numerous bog 
cholera bacteria in spleen as shown by a gelatine culture. A liquid cul- 
ture contains also butyric bacilli. 

No. 41, small black and white female, died yesterday. Post mortem 
changes under way. Large quantity of bload-stained serum in abdomen. 
Plastic peritonitis matting together the various organs; spleen enlarged 
and congested. Numerous old ulcers in ciecum and colon, with adher- 
ent slough. Adhesive pleuritis, with hirge quantity of blood-stained 
serum in thorax. Lungs normal, excepting areas of collapse in ventral 
and cephalic lobes. A liquid culture from spleen contains both hog 
cholera and butyric bacilli. A gelatine lube culture develops a large 
number of colonies in each needle track. 

December 10. — No. 42, small black and white male, died yesterday 
morning. No discoloration of skin. Spleen very large, congested. 
Lymphatics with cortex slightly reddened. Liver cirrhosed. A few ex- 
travasations in pyramids of kidneys. Mucosa of ciecum and upper 
colon covered with ulcers, the adherent slough dirty yellowish. Fully 
one-half the area of membrane thus involved, the remainder is pale. 
Lungs normal. From the spleen, hog cholera as well as butyric bacilli 
appeared in a beef infusion culture. In a tube of gelatine the colonies 
were very numerous. 

December 12. — No. 43, small black and white male, died December 10. 
No discoloration of skin. Spleen xery large, friable, gorged with blood. 
Iiigninals and lymphatics at lesser curvature of stomach hemorrhagic 
thioughout. Those of mesentery and mesocolon less so. A few 
petecchiaj on surface of kidneys. Liver slightly cirrhosed. Mucosa of 
csecum pale, of colon considerably congested. A few small ulcers with 
hemorrhagic border. Mucosa in fundus of stomach deeply congested. 
Slight hemorrhRge in principal lobe of each lung, otherwise both nor- 
mal. Bronchial glands hemorrhagic. Hog cholera bacteria quite abuu- 
dant iu spleen, as shown by cover glass preparations and cultures. 

December 15. — No. 44, medium-sized white female, died yesterday 
morning. Slight reddening of skin along median line of abdomen, limbs, 
and throat. Spleen enlarged and engorged. Inguinal, bronchial, retro- 
peritoneal and meso colic glands with cortex hemorrhagic. Liver badly 
cirrhosed. In crecum one ulcer an inch across, involving entire thick- 
ness of wall, and few smaller ones. A few in ujiper colon. Lungs 
aulematous. At least one-half of each lung (most dependent portion) 
airless, of a red flesh color. Sprinkled through it in some places more 
densely than in others are grayish-yellow areas one-half to two milli- 
meters in diameter. Trachea full of foam. Bronchi contain a thick 
mucous secretion, most abundant in the diseased region. A roll cult- 
ure from the spleen contains numerous colonies of hog cholera bac- 
teria. From a bit of lung tissue a rabbit was inoculated ; a plate culture 
from the same shows a very large number of colonies, probably hog 
cholera. The rabbit died on the seventh day. Spleen enlarged. Coagu- 
lation necrosis in liver, which also contains coccidia. Hog cholera bac- 
teria numerous in spleen, as shown by cover-glass preparations and roll 
cultures. 

. No. 45, large black-and-white female, died December 13. Slight red- 
dening of skin. Spleen large, congested. Lymphatics in general with 
cortex hemorrhagic. Liver badly cirrhosed ; surface dotted with hem- 
orrhagic points. Kidneys on surface and on section, as well as mucosa 
of cjv'cum and upper colon, dotted with numerous petecchiii'. No ulcer- 
ation. Large quantity of blood-stained serum and coagula in pleural 
sacs, chiefly in the right. Lungs not collapsed, iutiltrated with a red- 
15012 H c 4 



50 

dish serum ; left hypostatic. Abuiidaut mucous secretion in bronchi 
and smaller air tubes stained with blood. No hepatization. Roll cult- 
ure from a bit of spleen contains a large number of colonies of hog 
cholera bacteria. The same maybe seen in cover-glass preparations from 
the spleen itself. 

No. 4G. Large black-and-white male, died December 13. Spleen en- 
larged and congested. Abdominal lymphatics with cortex more or less 
congested. Liver slightly cirrliosed. One large ulcer on valve about 1 
inch across; several half as large in the middle of colon. Mucosa 
deeply congested in cfecum and colon ; much pale serum in pleural 
sacs. Lungs slightly cedematous. Of right lung the principal near 
root, ventral and tip of cephalic airless, collapsed. One lobule on ventral 
(diaphramatic) surface of principal lobe airless, with faint catarrhal in- 
jection of bronchioles and alveoli ; of left lung a small portion of the 
principal collapsed; the ventral and cephalic emphysematous. The 
trachea, bronchi, and branches contain a large quantity of a translucent 
viscid mucus; no lung worms present. Bronchial glands enlarged, pale; 
those on posterior aorta with cortex hemorrhagic. Extravasations 
beneath epicardium. A plate culture from a bit of lung tissue develops 
about seventy-five colonies of hog cholera bacteria. A rabbit inoculated 
from the same bit remains well. A roll culture from the pig's spleen 
contains about fifty colonies alike; one examined is made up of motile 
hog cholera bacteria. 

December 17. — No. 47, small female, died yesterday. Superficial in- 
guinals entirely hemorrhagic. Mesenteric glands slightly congested. 
Spleen barely congested. Mucosa of lower ileum com])letely ulcerated. 
Similarly that of csecum and upper colon, but more severely so as to 
make the intestinal wall very friable. In lower colon the ulcers are 
isolated. Lungs and heart normal. In a roll culture from a bit of 
spleen tissue about one hundred colonies of hog cholera bacteria ap- 
peared. 

No. 48, medium-sized black-and-white female, died last night. Suj)er- 
ficial inguinals enlarged, pale. Abdominal lymphatics in general 
with cortex hemorrhagic. Spleen congested; surface covered with 
numerous elevated blood-red points. Liver extensively cirrhosed. 
Mucosa of ileum dotted with petecchiie. It contains about fifteen ulcers, 
not limited to Peyer's patches, with longer diameter transverse, in some 
cases encircling the tube. The ulcer is covered by a thin yellow 
slougli. One ulcer, one-half inch across, in ciecum, and two in colon. 
About one-half pint of straw-colored serum and a mass of semi- 
gelatinous i)ale coagulum the size of a list in each pleural sac. Lungs 
but partly collapsed, pleura slightly roughened. Interlobular tissue of 
dependent lobes distended with serum, parenchyma cedematous, so as 
to sink in water. Bronchi contain a slight amount of reddish tiuid. In 
a roll culture from a bit of spleen pulp about two hundred colonies of 
hog cholera bacteria appear. 

Beeemher 24. — No. 49, large, black and white. Spleen gorged with 
blood. Lymphatics generally pale; liver cirrhosed. Ci^cum and colon 
with walls thickened and very friable; mucosa entirely ulcerated. One 
ulcer in rectum. A roll culture from the spleen melted, but found to 
contain on examination only hog cholera bacteria. 

DISEASE IN HEALTHY PIGS CAUSED BY MATERIAL FROM THIS EPI- 
ZOOTIC. 

A^ovemher 2L — Two pigs (Nos. 434, 435), about two months old, fed 
with spleens from several of the preceding cases. Two days later a few 



51 

more spleeus were given them. Both became sick a few days later and 
died November 28, about twelve hours apart. 

No. 434. Spleen slightly enlarged, full of blood. All glomeruli of kid- 
neys show as hemorrhagic points: lymphatics moderately congested. 
Stomach along entire fundus deeply congested. Superficial small ul- 
(;ers in ciecum and colon ; in the ciecum they are covered by a project- 
ing slough. Eight ventral and cephalic lobes collapsi'd, the formei" de- 
veloped into broncho pneumonia (catarrhal injection of small air tubes 
and alveoli). A few lobules of left priucii)al lobe in the same condition. 
Hog cholera bacteria in the spleen as determined by a gelatine and a 
liquid culture. A rabbit was inoculated with a bit of lung tissue and 
a plate culture made. This developed countless colonies, non-liquefy- 
ing, alike, shown to be motile hog cholera bacteria. Kabbit dies on sixth 
day. Spleen moderately congested; contains many hog cholera bacte- 
ria. In liver, minute foci of necrosis. A gelatine culture from the spleen 
contains numerous colonies of hog cholera bacteria. 

No. 435. Spleen enlarged, covered with hemorrhagic elevations. Kid- 
neys hemorrhagic as in No. 434. Stomach near pylorus deeply con- 
gested. CiECum and entire colon covered with a dirty yellowish and 
blackish slough. Eight and left ventral lobes, a small portion of right 
principal and left cephalic affected with bronchopneumonia. Cultures 
from the spleen of this animal were confused with those of another pig 
(No. 135), but one set remained sterile ; the other contained hog cholera 
bacteria, and it is highly probable that the fertile cultures belonged to 
this animal. 

A few additional cases are cited to show the infectious nature of 
this outbreak. 

No. 436 and No. 437 were placed, November 27, in the infected pen 
containing the two preceding animals. They were also fed portions of 
hog cholera viscera later on. No. 430 was found dead December 27. 
Eed blotches on skin of ventral aspect of body. Superficial inguinals 
hemorrhagic. Other lymphatics enlarged but p?-le. Spleen slightly 
congested. Mucosa of caecum and colon deeply congested and dotted 
with considerable number of small ulcers. A roll culture from the 
spleen melted, but contains only hog cholera bacteria according to mi- 
croscopic examination. No. 437 did not take the disease. 

No. 449 and No. 452, placed in the same pen December 17, but not fed 
with infectious matter, died December 29. The lesions were somewhat 
different from those usually found, and are briedy as follows: 

No. 452. Spleen and lymphatics not enlarged. Large quantity of se- 
rum and fibrinous coagula in abdomen. Viscera generally agglutinated. 
Lungs glued to chest wall by a recent exudate. Pericardium distended 
with serum and coagula. Lung tissue not affected. Kidneys deeply 
reddened. Mucosa of Ciecum and colon entirely covered with a thin 
layer of diphtheritic exudate ; when scraped away a deeply reddened 
surface is exposed. Numerous small, deep ulcers present. A roll cult- 
ure of si)leen,also melted from the heat of laboratory, contains only hog 
cholera bacteria. In No. 449 the lesions were the same, excepting the 
pericarditis. The ulceration of large intestine less extensive. 

Two very instructive cases of hog cholera were caused by simply ex- 
posing pigs on an infected asphalt floor in a pen adjoining cases of the 
disease. 

No. 404 and No. 400, about three and one-half mouths old, exposed with 
six others January 4. No. 404 died January 11. Superficial inguinals 



52 

noruial. Those in abdonieu much tumelied and lieniorrbagic tlirongh- 
ont. Si)leen enlarged, friable, with Leinorrhagic points. Several patches 
of mucosii in fundus of stomach one-fourth to one-half inch across, 
covered with blood clots. In large intestine oul}^ a few scattered petec- 
chiic on mucous membrane. Some subpleural hemorrhages in kings; 
lung tissue normal. Scattered petecchia) on epicardium of auricles and 
ventricles. On cover glass preparations from spleen pulp a moderate 
number of bacteria were present. In several roll cultures only colonies 
of hog cholera bacteria appeared. 

No. 40G died January 13. Skin of ears, throat, nose, limbs, and belly 
<leei)ly reddened. Spleen as in No. 4GJ:. A few petecchijv on epicardium. 
Kidneys as in No. 464. Urine contains blood. The mucosa of large intes- 
tine in general deeply congested and stndded with about fifty ulcers 
one fourth inch across. Meso-colic and retro-peritoneal lymjdiatics 
with cortex hemorrhagic. Stomach as in No. 464. Lungs normal, ex- 
cepting collapse of tw^o thirds of ventral lobes. EoU cultures from a 
bit of spleen pulp gave the same result as m preceding case. 

BRIEF SUMMARY OF THE IMPORTANT FEATURES OF THIS EPIZOOTIC. 

The high percentage of mortality in epizootics of bog cholera like 
the foregoing is the tirst thing to claim our attention. Out of 119 ani- 
nuds not less than 100 perished within the brief space of two months, 
or over 80 per cent. As no disinfection was resorted to, no isolation of 
the healthy attempted, it is difficult to say what number could have 
been saved. At any rate, the above figures indicate the mortality of 
this disease when left to itself, and it shows that nearly all young 
animals, such as weigh between 50 and 100 pounds, are susceptible to 
this disease. 

Most of the animals died rather unexpectedly. Only a con)paratively 
small number were visibly diseased some time before death. Since in 
many there was more or less ulceration in the large intestine, it indi- 
cates that animals may be in a very bad condition and become a source 
of inlection for others without necessarily showing it. 

The swill feeding has already been nnMitioned as a probable cause of 
the cirrhosis of the liver observed in so many of these animals. This 
organ was tough and imparted a gritty sensaiion totlie hand when cut. 
The parenchyma was softened and degenerated. It seems reasonable 
to suppose that this chronic malady may have made the herd more 
susceptible to the disease. 

Hemorrhagic lesions. — At least one-third of the cases examined showed 
lesions of a hemorrhagic character. The most common was an iutiltra- 
tion of the cortical portion of lymphatic glands with blood; sometimes 
the entire gland ajjpeared hemorrhagic on section. As regards the rel- 
ative frequency of this condition, the bronchial, posterior mediastinal 
(aortic), and inguinal glands stood first; next, the retroperitoneal, 
meso-colic glands and those in the lesser curvature of the stomach. 
The mesenteric glands were rarely affected. Accompanying this con- 
dition of the lymphatics was a very large spleen, its great size being 
simply due to an engorgement with blood. 



53 

Kext in frequency were the hemorrhagic lesions of serous niombraneS, 
in the form of puuctiform extravasations, larger ecchymoses, and very 
rarely of collections of blood infiltrating the muscular layers beneath 
the serous memhiane. Tliese extravasations were most frequent on the 
auricles and vetilricles of the heart, under the serosa of the large and 
small inl( flints, beneath the pulmonary pleura, and in the subcutane 
ous tissue. In the severest eases blotches appeared on the diaphragm- 
and costal p'eura. In about 10 per cent, the kidneys were hemor- 
ihagie. The glomeruli then appeared as minute blood-red points. To 
this may be added liemonhages in the pyramids and extravasations col- 
lecting around the i)apill{T;, 

The mueous membrane of the stomach in hemorrliagic cases was 
deeply reddened in the fundus; in some cases there was hemorrhage 
into the membrane, more rarely on the surface. The mucosa of the 
small intestine was usually intact, but that of the large intestine in the 
acute furm of the disease was in the same condition as the stomach. In 
older cases, when not covered with ulcers, it was either pigmented or 
dai k red, chronically congested. This outbreak was characterized by 
hemorrhagic lesions more than any other which we have examined. Our 
experience has been that the early cases are hemorrhagic and are suc- 
ceeded by those in which ulceration, cellular infiltration of the lym- 
l)hatics and signs of weakness, such as serous effusions, predominate. 

In some of the animals in this outbreak there were most extensive 
hf^morihages. In one the mucous membrane of the stomach was sepa- 
lated from the muscular coat by an extensive clot one-half inch thick. 
Ill five cases (10 per cent.) the lungs were the seat of extensive hemor- 
rhages, which literally converted the most dependent lobes into a blood 
clot and filled the pleural sacs with bloodstained serum. In a consider- 
able number both peritoneal and thoracic cavities contained much blood- 
stained serum. 

Ulcerative /c.s/oh.s.— Ulcers of the large intestine were present in 30 
out of 49 cases, or 70 per cent. They varied from ver^' slight to very 
severe and extensive lesions, involving in a small number nearly the 
whole mucous membrane of the caMUim and colon. The rectum was 
quite invariably free tVoin disease. The age of the ulcers can not 
be; determined, as the process of necrosis and subsequent ulceration 
seems to vary much in rapidity. In a few cases it was not limited to 
the mucous membrane, but extended into the muscular wall, produc- 
ing considerable local inflammation and thickening of the serous mem- 
brane. In rare cases the necrosis and cellular infiltration had made the 
intestinal wall so friable that it broke when handled. When the ulce- 
ration was slight it was frecjuently confined to the ileo-c;ecal valve and 
adjacent membrane, which consists of a large patch of l^-mpli follicles 
and some mucous glands. The ulceration in this situation was accom- 
panied by an extensive neojdastic thickening of the valve beneath the 
ulcer, indicating that the ulcer was old. In 5 cases (10 per cent.) the 



54 

lower ileum was ulcerated (Nos. 5, 21, 38, 47, 48) ; the ulcers seemed to 
have no relation to Peyer's patches. 

CompUcations. — Peritonitis, pleuritis, and pericarditis were not un- 
common conii)lications usually accompanying old ulceration. 

Lnng lesions. — This epizootic Avas studied mainly for the purpose of 
determining; the condition of the lungs in hog cholera. Swine plague 
is essentially a disease of the lungs, secondarily of the digestive tract, 
it may be i)ossible to find some cases of swine plague in which the 
large intestines are primarily diseased. Thus far they have not come 
to our notice. From the facts obtained from this epizootic we may 
safely assume that hog cholera produces no lesions which may not be 
found in the lungs of apparently healthy animals of the same age, and 
which may be due to the debility caused by the infectious disease. We 
must accept, however, the hemorrhages found in a small percentage of 
cases. Such are co existent with hemorrhages in most other organs, 
and are not specific lung lesions. (See Nos. 7, 17, 21, 22, 43, of autopsy 
notes.) The lesions found on imsimortcm examination were either sim- 
X>le collapse or lobular broncho pneumonia following it. 

Simple collapse usually involved the two ventral dependent lobes 
more rarely portions of the small cephalic and the principal lobes. The 
collapsed lobes, or groups of lobules interspersed among emphysematous 
lobules, appeared slightly, if at all, depressed. The color appro:, died 
that of red flesh. In only a few instances could plugs be found occlud- 
ing the bronchi. Sections made from lobules in this condition show a 
number of interesting features. The alveolar walls are crowded together 
in some places till they almost touch one another. Besides the fibrin, 
there may or may not be one or several large cells, round, with much 
protoplasm inclosing a vesicular nucleus. The bronchi are all open; 
the epithelium intact. The alveolar walls are not changed, nor is there 
any round cell infiltration to be seen. In circumscribed areas the capil- 
lary net-work is distended with blood corpuscles, while all the larger 
vessels are similarly filled with these elements. In the alveolar duct 
there is now and then considerable fibrillar fibrin well brought out by 
Weigert's stain. 

In about 15 per cent, of the animals examined one of the smaller 
ventral lobes was airless throughout and moderately enlarged. Viewed 
from the surface, the diseased lobe is bright red, dotted with minute, 
pale grayish or yellowish points of a diffuse hazy outline, each not more 
than 1 n.iiUimeter (J^ inch) in diameter. They are usually arranged in 
groups of four, and represent the ultimate air-tubes filled with cel- 
lular exudate. The larger bronchi are also occluded. The exudate is 
yellowish white, so firm tiiat it is possible to tear away the lung tissue 
with needles without necessarily breaking up the inclosed exudate. It 
may thus be teased out in the form of l)ranching cylinders, becoming 
smaller, and finally dwindliug down to the size of a coarse hair. 

In microscopic sections the alveolar walls are found beset with dis- 



65 

tended capillaries. The alveoli are filled up with cellular masses, fibrin 
appearing very rarely. In most alveoli the cells are large, round, with 
vesicular nucleus, cviilently derived from the alveolar epithelium. In 
some alveoli and in the smallest air-tubes the cell mass is so dense that 
individual elements can only be seen with dilliculty, but they appear 
to be identical with the cells just described. The process seems to be 
accompanied with very little inflammation. The desquamation and 
proliferation goes on in the alveoli and smallest air-tubes until they are 
occluded by the casts described. Of the 40 animals of the same herd, 
17 were found with collapse (Nos. 1, 7, 8, 12, 13, IG, 18, 21, 23, 24, 28, 32, 
34, 35, 41, 44, 4G), an(J eight with lobular bronchopneumonia (Nos. 2, 5, 
9, 14, 19, 22, 30, 37 ; see also Nos. 434 and 435). ]\rorc than one half, 
therefore, had some defect of the lungs. 

Ifcmightbe questioned whether such lesions as those of broncho-pneu- 
monia are not due to swine plague bacteria, since they closely resemble 
the appearance found in many swine plague lungs. This question is 
eflectually disposed of by the inoculation of lung tissue into rabbits. 
From IG lungs IG rabbits were inoculated. Of these lungs 8 were in- 
volved in simple collapse; 8 in broncho-pneumonia. Of the IG rabbits 
4 survived (Nos. 9, 18, 23, 4G) ; the remainder died of hog cholera 
(Nos. 2, 5, 12, 14, IG, 22, 28, 30, 34, 37, 44, 434). (The notes on these 
rabbits will be found in the autopsy notes of the swine as numbered.) 
Of the 4 survivors 3 had been inoculated from collapsed lung tissue, 
1 from a broncho-pneumonia. It is interesting to note that of these 
rabbits 1 died in six days, 4 in seven days, 3 in eight days, 2 in 
ten days, 1 in thirteen days, and 1 in fifteen days after inoculation. 
Plate cultures from the corresponding bits of lung tissue showed a vari- 
able number of colonies almost invariably non-liquefying, and in many 
cases identified as hog cholera bacteria. 

These facts lead to the inference that in hog cholera the specific 
bacteria will find their way to any diseased portion of lung tissue, and 
there multiply to a certain extent. In one case a plate culture from a 
bit of normal lung tissue showed but one or two colonies, while a bit of 
collapsed tissue from the same lung showed a large number. There is 
no doubt that the slight exudate and feeble circulation in collapse and 
the abundant partly cellular, partly mucus or fibrinous exudate into 
the air spaces in broncho-pneumonia furnish a favorable nidus for 
jiathogenic bacteria. These may have been carried there by the blood or 
they may have been introduced from without. If the latter supposition 
l)rove true, and there are no valid objections to it, diseased lungs in 
hog cholera may not only become the means of disseminating the dis- 
ease through the mucus and expired air, but they may become the chan- 
nel, the weak spot, through which the virus enters the organism. 

To elucidate this question, if possible, the following instructive ex- 
periment was made : 

Two pigs (Nos. 4G0 and 4G1), about ten weeks old, received each into 



56 

the right iuug, December 21, 3 cubic centimeters of a beef-infusion pep- 
tone culture two days old, inoculated from a single colony growing in a 
roll culture. This had been made from a bit of spleen tissue from No. 
40 of the outbreak described iu the preceding pages. There were about 
fifty colonies in the tube, all alike. To test the culture, a rabbit received 
at the same tiaie one ninth cubic centimeter snbcutaneously in the thigh. 
It died in five days. The spleen was much enlarged, blackish, friable, 
and contained hog cholera bacteria. A roll culture contained numerous 
colonies after two days. The liver contained no centers of coagulation 
necrosis, as the animal had succumbed too quickly. 

Ko. 400 became very weak in its hind limbs in less than a week; res- 
pirations short and quick; bowels relaxed. It was found dead on the 
ninth day. Superficial inguinal glands normal. Petecchiaeiu the slight 
deposit of fatty tissue beneath peritoneum of abdominal muscles. 
Spleen about 12 inches long, IJ inches wide, and three-fourths inch 
thick at the hilus, blackish, friable. A few petecchijie on cortex of 
left kidney. One cyst, the size of a large pea, In medulla. A large 
number of small hemorrhages iu connective tissue around pelvis of 
right kidney ; five small urinary cysts not showing on surface. Glands 
in lesser omentum eidarged, hemorrhagic throughout. In crecum and 
colon an almost continuous yellow sheet of superficial necrosis, about 1 
millimeter thick, covering the mucosa. In lower colon it breaks up into 
isolated patches, simulating ulcers. In microscopic sections this layer 
is found to consist of necrosed epithelium intermixed with some round 
cells. On Peyer's patches iu lower ileum a yellow, soft deposit rests^ 
which is not adherent and might be mistaken for chyle. Lobes of right 
lung glued together aud to pericardium. Pleura thickened generally ; 
serum very slight iu amount, blood stained. On lobes of left lung, 
which are also glued together,. aud on right lung, tliere is a very slight 
deposit, about one-half millimeter thick, in the form of a net work. 
The pleuritis and exudate is most marked ou the most dependent por- 
tions of the lungs. Cavity of pericardium normal. Lung tissue not 
hepatized anywhere; trachea and bronchi contain a small quantity of 
reddish fluid. Bronchial glands and those along i^osteiior aorta hem- 
orrhagic throughout. Cultures from pleural cavities, as well as. those 
from spleen, contain only hog cholera bacteria. As shown in roll cul- 
tures they were very numerous iu the latter organ. 

While No. 400 presented such a well-marked case, No. 401, although 
presenting at first the same symptoms, slowly recovered. The differ- 
ence may have been due to the fact that with No. 400 a G-inch needle 
was used, while with No. 401 one only 3 inches long. In the latter case 
the chances for the passage of bacteria into the lung tissue and thence 
into the intestines were much poorer. 

On July 31, over seven months after inoculation, No. 401 was found 
dead. It had continued well and thrifty, and no more attention had 
been paid to it. Only the lungs and the liver were brought to the lab- 



57 

oratory, since all the other organs, including the digestive tract, were 
rei)orted normal, exce])tiiig the kidneys, which were said to be highly 
congested. 

Lungs, bat slightly colhipsed, dark red. Cei)halic and ventral lobes 
of boili hings and tlie nzygos lobe solid to the touch, f a grayish red 
color, with tortuous injected vessels under the pleura. On section, the 
tissue cuts like cold meat. Color grayish to (hirk red. The cut ends of 
bronchi show plugs of a glairy mucus. The marginal i)oition of the 
lobe is grayish, homogeneous, very dense. Towards the center of tiie 
lobes the tissue is nu)re reddish, infiltration not so dense, and speckled 
with small masses (one-half millimeter across) of a yellowish-white, 
homogeneous, cheesy matter. On the border of the right cei)lialie lobe 
an encysted mass, clieesy, yellowish, gritty to the knife, evidently the 
result of the inoculation. There were reported adhesions of the dis- 
eased lobes to chest wall, indicative of pleuritis. 

Bronchial glands slightly larger than walnuts, of a uniform grayish 
<lense texture. Trachea and bronchi occluded with a blood clot of very 
recent origin. In the extremities of the large bronchi lung-worms em- 
bedded in the clot. 

Heart of normal size, rather llabby. Both auricles and the attached 
vessels filled with tarry semi coagulated blood. In left auricle a white 
clot also present. Left ventricle firmly contracted. 

Liver small; surface roughened witli adherent fiakes of tissue, indi- 
cating old perihepatitis. Parenchyma tough, resembling in texture 
very soft rubber. Acini witL dark center and pale bloodless peri])hery. 

The immediate cause of death was imlmonary hemorrhage; the re- 
mote cause, the bronchopneumonia caused by the inoculation. The 
lung worms aggravated the lesions already present. What is most in- 
teresting in this connection is the fact that hog cholera bacteria were 
still present in the lung tissue, as the following will show : 

Three roll cultures made from bits of lung tissue; the developing 
colonies all alike and resembling those of hog cholera bacteria; no 
liquefying colonies in any tube. Beef infusion cultures from the indi- 
vidual colonies demonstrate the identity of the bacteria with those of 
hog cholera. A rabbit inoculated with sterile beef infusion, in which a 
bit of lung tissue had been torn up, remained alive, while another rab- 
bit, inoculated from the pure culture made of the colonies of the roll 
culture, died in six days with enlarged spleen, coagulation necrosis in 
liver, extravasation in lower large intestine, and many hog cholera bac- 
teria in spleen. Cultures from blood and spleen pure. 

The lung disease in thisaninnil could not have been more than three 
months old, and was very likely due to the injury to lungs resulting 
in adhesion to chest wall and the inflammation around the encysted 
mass. 

This experiment shows (1) that hog cholera bacteria, when intro- 
duced into the lungs, do not produce a specific parenchymatous inflam- 
mation of themselves ; (2) that the}^ may pass from the lungs by way 
of the pharynx into the digestive tract and there produce their charac- 
teristic effect. 



5» 

Bacteriological observations. — The precediug experiments on rabbits 
and tlie intrathoracic inoculation in case of the pigs are snflQcient of 
themselves to establish the fact that the bacteria described in the re- 
ports of the Bureau for the years 1885 and 188G, and again found in this 
epizootic, are the cause of hog cholera. It may be added, however, 
that out of fifty-six cases (here rei)orted) hog cholera bacteria Avere 
found in the spleen of all but six. Even in these the cultures made 
were too few to make the negative evidence of any value. 

In many cases the hog cholera bacteria were associated with a rather 
large bacillus, which, for the sake of convenience, we will call butyric 
bacillus.* This organism was only detected when a bit of spleen was 
dropped into beef infusion, with or without peptone. The culture, kept 
at about 35° C, contained on the second and third days a cloudy mass 
limited to the bottom of the tube. The cloud was made up of bacilli, 
rather large, with a spore in one extremity of the rod strongly refract- 
ing the light. The rod was not enlarged at this end in the fresh state. 
^\ hen dried and stained, the shrunken protoplasm gave the spore bear- 
ing end a swollen ajipearance, reminding one of the tailed bacteria of 
okler writers. In the few tubes in which this bacillus alone was pres- 
ent the liquid itself remained perfectly clear; when liog cholera bac- 
teria were present, it became uniformly but faintly clouded. In liquid 
cultures, without the bit of spleen, the bacilli did not develop. This 
was evidently necessary as food material. In gelatine-tube and roll 
cultures the bacilli did not grow. They are very likely anaerobic or- 
ganisms, abundant in the alimentary tract, and absorbed from ulcers 
or lesions of blood-vessels into the circulation before death, in the spore 
state, and their development kept in check until that occurs. It is also 
probable that they are important factors in the rapid changes which 
may take place after death. They are quite constantly found in the 
liver of different animals wlien post mortem changes have begun to de- 
velop. 

in some half dozen cases decomposition was so far advanced that no 
thorough examination was made. At first it was thought that the ani- 
mals bad been dead several days, but the person in charge of the herd 
asserted that they bad died during the night. Although the tempera- 
ture had fallen below 30° Fahrenheit (1° C), decomposition was far 
advanced. It may be that the live animals crowded upon the dead 
and thus kept the bodies warm. Yet this supposition is not capable 
of accounting for the rapid changes. The hemorrhagic lesions may have 
enabled various bacteria to become distributed throughout the body. 
The heat disengaged by them during multiplication, aided by the body 
heat of the animals still alive, may have been sutficient to keep up the 
process of decomposition, This^os^ mortem growth maj' also account 
for the large number of hog cholera bacteria found in many spleens, 

* Whether this bacilhis is identiccal with the bacilhis of malignant oedema, as has 
been asserted by some, I do not kno'w, as no experiments were made to test its path- 
ogenic power. 



59 

although the temperature of the air was far below the point where mul- 
tiplication may take place. 

In the foregoing" ei)izootic, as well as in those studied in 1885, and 
]88G, there was no difficulty whatever in demonstrating the presence 
of the hog cholera bacillus in the spleen. The herd referred to in the 
l)receding pages was swill-fed, and the animals were ver}' likely crowd- 
ing each other more or less, not being compelled to hunt lor food. 
Hence each oue was exposed to a large quantity of virus. The same 
may be said of the penned pigs at the Experiment Station. The dis- 
eased animals found in different localities were brought to the station 
and penned with healthy ones. A severe epizootic was quite invariably 
the result, owing to the unusually good opjjortunity for infection in the 
pens aud the saturation of the floors and soil of the pens with virus. 

When swiue roam over a considerable extent of territor^^ in search 
of food, the virus is more widely distiibuted but less concentrated, 
Less virus is therefore taken ni> by individual animals, and although 
the disease is equally fatal in the end, the course may be somewhat 
different and the lesions less extensive. At the same time the bacte- 
ria may elude observation. They may remain more or less localized, 
owing to the reactive power of the organism, which destroys those that 
have entered the internal oigans. To those who would give up the 
search for hog cholera bacilli after a few unsuccessful attempts to find 
them, we would reccommend the perusal of the following three cases, 
after having reviewed the epizootic just described: 

Hog cholera prevailed more or less in Montgomery County, Mary- 
land, during the latter weeks of September and the early part of 0(;- 

tober, 1888. October 17 Mr. H lost about 22 out of a herd of 55 

to <50 swine during the past four weeks. Of those now scattered in a 
large held 2 a])[)ear ill ; 1, a small black shoat, is killed by cutting its 
throat and examined. The superficial inguinal glands are very much 
enlarged, the surface mottled, dark red. The spleen large, but pale 
and rather firm. The liver shows signs of invasion of the sclerostoma 
pingiiicoJu. The lymphatic glands i\i lesser curvature of stomach are 
very large ; cortex completely hemorrhagic. 

The left lung normal ; the principal lobe of the right lung has in it 
a mass of tissue involved in broncho pneumonia, extending obliquely 
from the free border to near the dorsal region, about 1 inch thick; 
the lymphatics along the dorsal aorta are likewise hemorrhagic; the 
stomach tilled with food ; small intestines contain a number of attached 
cchmorhynchi; the large intestines distended with semi-i^'olid fecal mat- 
ter; the mucosa in general is normal, but in the caecum are two ulcers 
about three eighths inch across, round, slightly elevated, with center 
black and periphery yellow; beneath the superficial slough is a 
whitish, firm, new growth, extending to the muscular coat in the center 
of the ulcer. 

The spleen and the right lung were taken to the laboratory. From 
the former cultures were made on agar, in gelatine and beef infusion, 
by adding bits of spleen tissue as large as i)eas. In no tube did any 
development take place. A rabbit inoculated by tearing up a piece of 
hepatized lung tissue in sterile beef in fusion and injecting the turbid 
liquid subcutaneously remained well. 



60 

Several miles from the first farm we came upon a herd of young pigs 
which were just showing signs of disease, althougli none had been lost. 
One of them, with unsteady gair, which hid in the litter under a shed 
and returned to it when driven away, was killed by bleeding from the 
vessels of the neck. The lungs were without a sign of disease. Spleen 
enormously enlarged and gorged with blood. The lymphatic glands of 
groin and about stomach very large but rather pale, and oedematous 
on section. Stomach filled with food. Large intestines overdistended 
with very dry, hard feces, somewhat softer near caecum ; in the latter 
only one ulcer and this on the valve, about one-fourth inch across and 
of the same nature as the one found in the preceding case. 

A portion of the spleen of this animal was taken to the laboratory 
and cultures made, as in the previous case, with bits of spleen, AH 
cultures remained permanently sterile. 

Several miles from the latter place we found the disease on a farm 
situated on a hill. The swine were allowed to go a considerable dis- 
tance down the slope to a marshy stream. The owner had lost or 8 
out of a herd of 20 to 25 within six weeks. A few were evidently ill, 
but none were killed, as a dead one was found. It had probably died 
during the night. The buzzards had consumed nearly all the intes- 
tines through a small hole near the pubis. Putrefaction had already 
set in. Spleen enlarged, slightly congested. In the small portion of 
the large intestine, which still remained, an ulcer was found three- 
eighths inch across. The glands of lesser omentum with hemorrhagic 
cortex. The stomach contains a small quantity of bile stained lluid. 
Both lungs glued to chest wall by coagulated fibrin from blood extra- 
vasation. Left lung contains about ten to fifteen hemorrhagic foci, 
visible under pleura, one-fourth to one half inch across. The principal 
lobe of right lung solid, granular, involved in broncho-pneumonia. The 
hepatized lobe was discolored by recent and extensive blood extravasa- 
tion. A gelatinous deposit under sternum resting on pericardium. 
The semi-decomposed condition of the animal i)revented a mor.' careful 
examination. Portions of the spleen and hei)atized lung tissue were 
taken for examination. 

While the spleen of the two preceding cases showed no indications 
of bacterial life on cover-glass i)reparations, the s[)leenof this ease con- 
tained a considerable number of bacteria resembling hog cholera bacilli 
very closelj". On gelatine they grew differently from the latter, and 
the cultures emitted a slightly offensive odor. In liquids they were 
actively motile. They were putrefactive bacteria, without effect upon 
two rabbits inoculated with large quantities of the cultures. A rabbit 
inoculated with the diseased lung tissue remained well. The latter on 
closer examination had a texture as granular as the roe of fishes, the 
granules being inspissated cell masses in the alveoli and air tabes. At 
least four different kinds of bacteria were present in large numbers. 

The absence of bacteria from the spleens of Nos. I and 2 is in har- 
mony with the results obtained in other infectious maladies when ani- 
mals are killed in the early stages or during the height of the disease. 
It is only in the last stages that the bacteria become most numerous and 
appear in sufficient numbers in the internal organs to be easily detected. 
In the third case, death was very likedy brought on by pulmonary hemor- 
rhage not infrequently found in hog cholera. The specific bacilli pro- 
duced at first the ulcers, and were either working their wa^' slowly 
into tlie, internal organs or else were being destroyed in the ulcer itself. 



61 

The latter termination would signify recovery; the former death. These 
ulcers might be aptly compared to the malignant pustule in man, in 
which the virus remains at first localized but may spread throughout 
the system after a time. The presence of numerous ulcers in swine in 
the first epizootic is to be regarded as a multiple infection, while in tlie 
three cases just cited the infection was limited to a few foci or but one. 
The ulcers would no doubt have revealed the virus, but ouri^revious 
experience with spleens of diseased swine made it seem unnecessary to 
study the ulcer itself. As regards the lung disease of the third case, 
notliing positive can be said. It resembles most closely chronic swine 
plague. The germ of this dis<'ase was not present, however, as shown 
by the rabbit inoculation. 

Buzzards may carry the disease from one place to another. When 
the dead animals are at all exposed to view they are immediately at- 
tacked. Whether hog cholera bacteria are entirely destroyed in the 
digestive tract of the birds can not be said, but there is nothing in the 
range of our knowledge of bacteria which will exclude the probability 
that the bacteria are not all destroyed during the process of digestion, 
and that they may be distrilmted by these birds from place to place in 
the discharges. 



THE CAUSATION OR ETIOLOGY OE HOG CHOLERA. 

The suspiclou eiitertajiied by those engaged in the study of diseases of 
mau aud the lower animals that infectious or communicable diseases 
are due to living organisms ot the lowest order, capable of rapid multi- 
plication by the process of fission and spore-formation, has been trans- 
formed into conviction during the past ten years. A considerable num- 
ber of the most common, most dreaded diseases have been proved to 
be caused by exceedingly minute, plant like organisms known under 
tlie general name of bacteria. Among animals the microorganisms 
causing anthrax, black quarter, tuberculosis, glanders, strangles, infec- 
tious pneumonia in horses and swine, and roiujet in swine have been 
very thoroughly demonstrated. The opinion has been steadily gaining 
ground that in order to control infectious diseases we must learn their 
causes and the life history of the pathogenic bacterium found in each 
disease. These will suggest to us the measures that are most likely to 
prove successful in combating such maladies. Moreover, it is pretty 
well accepted to day that the prevention of infectious diseases is the 
main thing to be arrived at in our studies, and that their treatment 
when they have ouco obtained a foothold is at best tentative and rarely 
successful. This is especially true of the lower animals. They cannot 
be treated with the same care which is accorded to human beings at- 
tacked by infectious diseases, They are (in some diseases at least) 
always scattering the living virus and thereby endangering those still 
free from disease. 

In the investigation of swine epizootics these facts have been care- 
fully borne in mind, so that most attention has been paid, first, to the 
life history or biology of the micro-organism 5 second, to disinfectants 
as de^troyer^)of the specific bacteria; and third, to the various methods 
of preventive inoculation. 

THE BACILLUS* OF HOG CHOLERA. 

During the past three years the number of swine affected with this 
disease which have been examined is about 500. About three-fourths 

* The term bacterium, implying a form genus between micrococcus aud bacillus, has 
been almost wholly given up by bacteriologists, and all those forms classed under 
bacteria have been thrown together under the genus bacillus. This change is un- 
fortunate for several reasons, inasmuch as many species were best classed under the 
genus bacterium. This latter term, which was applied to hog cholera microbes in the 
reports of 18d5-'c6=^'87, is iiow relnctoutly given up for the sake of uniformity. 

G'J 



64 

of tliis iiiuuber died at the experimental station of the bureau. The 
remainder came from outbreaks of the disease within 2 or 3 miles of the 
Station. Besides these, a small number of animals were examined in 
some of the Western States. From perhaps 400 the same microbe was 
obtained, there being practically no diflerence between the pathogenic 
microbes obtained from all the outbreaks thus far investigated. 

Of the internal organs the spleen contains the largest number of 
bacteria, and in acute hemorrhagic cases they are sufficiently numerous 
to be detected on cover-glass preparations. A minute bit of spleen 
pulp is rubbed on a cover glass, dried and heated according to the ac- 
cepted methods, and then stained for a few minutes in an aqueous so- 
lution of methyl violet. The bacteria then appear as elongated ovals 
or short rods with rounded ends, chiefly in pairs. When the staining 
has been very brief only the periphery of the rod is deeply stained, the 
central portion being pale and simulating the ai)})earance of an endo- 
spore. When the period of staining is prolonged to half hour or more, 
the rod may become uniformly stained. 

Bacteria thus dried on a coverglass and mounted in balsam measure 
from 1.2 tol.5, occasionally 1.8 micro-millimeters (.OOUOo-.OOOOG iiicli) in 
length, and about .G micro-millimeter {. 000024 inch) in breadth. 

In sections of the s[)leen from acute hemorrhagic cases the bacilli 
may be found in considerable numbers. Sections were hardened in al- 
cohol, cut dry, and subsequently stained with aniline water meth.yl 
violet. They were in some cases decolorized in 1 per cent, acetic acid. 
The bacilli then appear as short, plump rods, uith ends rounded otf; 
sometimes they are short enough to deserve the name of ovals. The 
periphery is more deeply stained than the central body of the rod. 
They measure on the average 1.5 micro-millimeters. In such sections 
the bacteria appear in small masses in the capillary spaces of the 
spleen -pulp, rarely among the cells of the malpighian corpuscles 
(Plate X, tig. 2). The masses appear more or less star-shaped. The 
bacilli are crowded together in the center : from this, linear groups ra- 
diate inio the cai)illary network. Such masses may be 8 to 10 micro- 
millimeters in diameter. They are fairly numerous in spleens from 
acute cases. That the size of these colonies is not due to postmortem 
nuiltiplicatiou is shown by the fact that the largest and most numerous 
colonies were found in the spleen of an acute case which was examined 
within two hours after death, in the month of November. 

In sections of ulcers hog cholera bacilli have been searched for, but 
the examination of a large number of ulcers showed that no positive 
results could be obtained. Different ulcers showed different bacteria, 
sometimes large colonies of micrococci, sometimes groups of large ba- 
cilli, following the course of the blood-vessels in the embryonic tissue 
under the slough. These no doubt found their way in from the super- 
ficial slough which seemed to be made up almost entirely of bacteria. 
Moreover, hog cholera bacilli closely reseujble ijiany putrefiictive forms, 



G5 

so that even if they could be readily seen nothing- but a good diflfer- 
eutial stain would enable us to recognize tbem. That they are present, 
however, may be demonstrated by inocuhiting mice or rabbits with bits 
of the ulcer. A small number of mice may succumb to malignant oedema. 
The rest will die of hog cholera. In rabbits the local effect of such 
inoculation is usually quite severe, owing to the putrefactive bacteria 
introduced at the same time. 

Stainingof hog cholera bacteria, — On cover-glass preparations they are 
easil^^ brought into view by a few minutes' contact with water}' solu- 
tions of the ordinary aniline colors, such as methyl violet, fuchsin and 
methylene blue. Decolorizing agents, such as acetic acid, one-half to 
1 per cent, must be used carefully lest the color disappear from the 
bacilli also. When stronger dyes, such as alkaline methylene blue orani- 
]ine water fuchsin, are employed, the bacilli are decolorized with greater 
difficulty. Watery solutions should therefore be employed only for 
cover-glass preparations where decolorizing is unnecessary-. Forsections 
it is well to harden tissues in alcohol. The sections may be stained 
with Lofder's alkaline methylene blue or with aniline water methyl 
violet or fuchsin for from one-half to one hour. After a a few seconds' 
contact with a 1 per cent, solution of acetic acid they are washed in 
water, then passed through alcohol, turpentine, or xylol or cedar oil, and 
mounted in xylol balsam. Xo stain which differentiates these bacilli 
very sharply from others has been found. They are decolorized when 
the method of Gram is employed. 

Distribution of bacteria in the body.-^This can be best determined by 
the delicate method of cultivation. In acute cases the spleen contains 
the largest number. In coverglass preparations of spleen pulp there may 
be. four or five in every field of the microscope. In general, the liver 
contains almost as many bacteria as the spleen. The lungs, lymphatic 
glauds, and kidneys may also contain them in moderate number. They 
are fewest in blood from the heart (right ventricle). In slow, chronic 
cases, characterized by slight ulceration of the large intestine, the 
number of bacteria in the internal organs is very small. From the 
spleen of such cases cultures are made fertile only by using bits of tissue 
as large as split peas. 

Whcu it is of importance to make a diagnosis from a chronic case it 
might be well to adopt the method suggested byFriinkeland Simmonds 
for typhoid fever. They wrapped the spleen in cloths wet with a solu- 
tion of mercuric chloride and placed it in a warm room for twenty-four 
hours. The bacilli of ty[)hoid, capable of multiplying in the organs 
after death when the temperature is not too low, became suflScieutly 
numerous to be readily detected in sections. The same may be said of 
hog cholera bacilli. It must, however, be borne in mind that in chronic 
cases other bacteria may have gained entrance into the body and appear 
in the spleen. These, multii)lying at the same time, may give rise to 
erroneous inter[)retations. 
15G12 II c 5 



66 

When the destruction of the mucous membrane in the large intestine 
is extensive, bacteria of various kinds may be found in the peritoneal 
cavity. The serum collected often contains several varieties of organ- 
isms, and when sections are made of the walls of the peritoneal cavity 
micrococci and bacilli are seen resting in a thin layer upon the perito- 
neum. Sometimes the pleural fluid, and still more rarely the pericar- 
dial fluid, may give rise to cultures of micrococci. These resemble the 
micrococci, causing suppuration in man {stajphiilococci) in their appear- 
ance and mode of growth in gelatine. The presence of anaerobic bacilli 
in spleen and liver has already been dwelt upon. The presence of bac- 
teria in the peritoneal cavity is easil}' explained by their passage through 
the ulcers in the intestines. It is a fact worthy of note that only very 
rarely bacteria other than those causing the disease were encountered 
in the spleen and the circulation. Perhaps those causes or agents which 
destroy bacteria are less active in the serous cavities than in the blood 
and spleen. The various complications of chronic ulceration already 
mentioned, such as peritonitis, pleuritis, and pericarditis, are without 
doubt due to this secondary invasion of bacteria, which have the power 
to produce inflammation of serous membranes. It need not be said 
that in the earlier investigations, when little was known of bacterial 
diseases, the explanation of the presence of these microbes was very 
perplexing and misleading. 

Biology of the hog cholera bacillus. — The cultivation of bacteria in nu- 
trient media outside of the animal body serves two distinct purposes: 
(1) The diagnosis of specific forms so that they may be easily recognized, 
and (2) the study of their biology or life history. 

a. Diagnostic characters. — Hog cholera bacilli are not readily dis- 
tinguished from a large number of other bacteria found in surface 
waters and in the superficial layers of the soil, either in their form or 
in their manner of growth in culture tubes. The more minor difteren- 
tial characters we can therefore obtain, the more certain our diagnosis 
will be. For this end the hog cholera bacillus was cultivated in as 
many media as were available. 

If a bit of spleen pul[) from swine which have succumbed to hog 
cholera be thoroughly shaken up in a 10 per cent, beef infusion peptone 
gelatine, liquefied by a gentle heat, and the whole poured upon a sterile 
glass plate protected from the dust by a bell glass and allowed to con- 
geal, colonies of hog cholera bacilli will a])pear within forty-eight hours 
as mere specks to the naked eye. Examined under a low power they 
are spherical, with sharply defined border. The disk of the sphere is 
homogeneous without any concentric markings, and of a brownish 
color. This description applies to colonies beneath the surface of the 
gelatine layer. Colonies which grow on the surface soon spread out 
into thin pearly layers several times the size of the deep colonies, and 
roundish or irregularly polj^gonal in outline. 

Besides the deep spherical and the flat surface colouies there is oc- 
casionally a third form present. This is a ver^- faint cloud like colon^y 



67 

growiug between the glass plate and the gelatine, si)reacliug as a very 
thin layer laterally and attaining the dimensions of a snrface colony. 
Many snch colonies have spherical prolongations upwards into the gela- 
tine layer so as to assume the form of a lid with a knob like handle at- 
tached to its center. It is very probable that the colony begins as a 
sphere in the gelatine layer near its lower surface. As soon as it 
touches the glass, by virtue of its enlargement, spherically, it spreads 
out into the attenuated, cloud-like layer. Such colonies are rare, ex- 
cepting in so-called line cultures made by drawing a platinum wireacross 
the gelatine layer before it has congealed. 

Perhaps the best device for studying the growth of such colonies is 
the Esmarch roll culture.* The gelatine, coating the inside of the test 
tube, is protected from contamination and desiccation for a long tinie. 
The colonies have thus the opportunity of expanding to their utmost 
capacity. In a roll culture ten days old, for example, the deep colonies 
W'Cre about one half millimeter in diameter, perfectly spherical, the disk 
homogeneous, yellowish white, when viewed with a hand lens. Under 
a 1-inch objective it appeared reddish brown, with no markings. The 
surface colonies in the same tube were about eight times as large, i. e., 
4 millimeters across. They presented centrally an opaque white patch 
or nucleus, outside of this a more translucent zone, beyond this another 
opaque zone, and lastly a limiting transUicent border. The colonies 
were irregularly i)olygonal in outline. The alternation of thin and thick 
zones was very likely due to the variation in .temperature to which 
gelatine cultures were exi)osed in a badly heati d laboratory, for they 
are by no means always present. (Plate XI, fig. 2.) 

Tube cultures, made by piercing the gelatine in a test tube with a 
l)latinum wire previously forced into the spleen, show minute yellowish- 
white spheres in the track of the wire in forty-eight hours. These rarely 
exceed one half millimeter even after several weeks. The snrface 
growth spreads from the place of inoculafiou as a thin pearly layer of 
variable thickness, ev( ntually becoming 4 to G millimeters in diameter; 
under especially favorable conditions of temperature, etc., it may be- 
come still larger. ^Vhen the inoculated bacteria are very numerous the 
growth beneath the surface appears as a solid yellowish-white track, in 
which the colonies have become fused together. The gelatine is at no 
time liipietied. The bacilli grow somewhat larger in gelatine than in the 
body of diseased animals. Occasionally filaments of considerable 
length are met with, and in general irregular, involution forms are not 

" These roll cultiu-es are made as follows: The gelatine, luiueticd l)y j^entle heat in 
the tube iu which it was sterilized, is inoculated with the tissue, Idood, urine, or any 
lir|uid containing bacferia, and carefully stirred up. A second culture uuiy be made 
from the first by transferring from it with a platinum loop some of the liquid gela- 
tine. This is done when the number of bacteria in the lirst tube may be too numer- 
ous. A rubber cap is litted over the month of the tube after replacing and trimming 
the cotton- wool plug, and the tube i)laced horizontally iu ice water and rolled about 
its long axis until tlie inside of the tube is coated witli a uniform layer of congealed 
gelatine. The tube may also be rolled on a smooth block of ice, a method which I 
first saw in the Pathological Laboratory of Johns Hopkins University, and which is 
very useful when rubber caps are wanting, or when it is desirable to licep the phig 
free from gelatine. 



68 

uncommon. When a bit of spleen tissue is rubbed upon iin inclined 
surface of agar agar in a culture tube, isolated colonies make their ap- 
pearance within twenty-four hours as circular, grayish-white, semi- 
translucent, very flat cones 1 to 2 millimeters across. When the ba- 
cilli are very numerous a slight prick of the spleen pulp with a platinum 
wire is sufficient. Otherwise the too numerous colonies will coalesce 
into a grayish, shining, semi-opaque layer of scarcely perceptible thick- 
ness. Its appearance on a^rtrcan not be distinguislied from the growth 
of typhoid bacilli and a number of saprophytic bacteria. On blood 
serum the growth a^ipears as a very thin, grayish, translucent layer. In 
bouillon, either with or without peptone, the bacilli grow rapidly enough 
at 80° to 95° F. to produce a slight opalescence within twenty-four hours. 
This does not increase in density subsequently. There is no membrane 
formed on the surface of the liquid. When standing undisturbed for 
one or two weeks, a white ring-like deposit of bacteria frequently forms 
around the tube at the surface of the culture liquid. There is only a 
very slight deposit formed, showing that multiplication in liquid media 
comes to an end within a few days. 

The length of the bacilli in bouillon is about .9 micromillimeter, their 
width .4 to .5 micromillimeter, therefore somewhat smaller than in 
the spleen. When examined in a drop of bouillon suspended from the 
under surface of a cover-glass in a " cell," the bacteria are seen to be 
motile. Taken from cultures one or two days old thej^ execute very ac- 
tive spontaneous movements. Their movement is one of rotation as 
well as translation. They quite invariably occur in pairs, and the 
movement of rotation is about their point of union as an axis. The pairs 
of bacilli as they shoot across the field have thus an oscillating motion 
at the same time. The bacilli do not come to rest at all, but swarm 
about very rapidly until the liquid is dried up. 

Though this motility is most marked in recent cultures, it may still 
be seen at the end of one or two weeks in most liquid cultures. 

The same active motion is observed in bacilli taken directly from the 
animal, such as the spleen of rabbits, which have succumbed to inocu- 
lation. If a bit of spleen tissue be rubbed in a drop of sterile water 
on a cover-glass and the whole examined as a hanging drop, in one or 
two minutes the bacilli become as active as in cultures. 

Growth on boiled potato, when at 95'° F., appears as a faint straw- 
colored deposit within tw^enty-four hours after iuoclution. At 20° to 
25° C, it appears one or two days later. It slowly spreads in all direc- 
tions as a layer of perceptible thickness. The color changes to a dark 
brick red, or may remain whitish. In general the growth is darker the 
more rapidly the potato dries up. 

The growth is also restricted by drying. In some sultures it has 
covered almost the entire cut surface of the potato. In others it re- 
mained as a broad band over the line of inoculation. The bacilli multi- 
ply very abundantly in milk without producing any alteration visible 
to the naked eye. 



G9 

Tlio diagnosis of hog cholera bacilli may therefore be made by taking 
together the following morphological and biological characters : (1) 
Short bacilli with rounded ends, or ovals, readily stained in aqueous 
solutions of aniline dyes. (2) Growth at GS^toSCP F., on gelatine, with- 
out producing liquefaction. (3) A rather feeble growth in beef infusion 
coupled with active spontaneous movements. (4) Growth on t'lc cut 
surface of boiled potato at ordinary temperature as well as in the incu- 
bator, (o) Active multiplication in milii without any macroscopic 
changes. (G) Growth in racuo. (7) Absence of any odor arising from 
the cultures. (8) Fatal effect on rabbits, guinea-pigs, and mice when 
inoculated. This will be discussed later on. 

These characters are emphasized, since we have several times found 
bacteria in the internal organs of swine which may have many points 
in common with hog cholera bacilli; especially as regards their form, 
motility, and growth in gelatine. In fact in w;is quite impossible to 
decide until inoculations upon animals were m;ule. The absence of 
pathogenic power was thus made the chief critei ion. 

{!)) Other plujsiolooical characters. —Though alkaline media are as a rule 
most favorable for bacterial multiplication, yet there is a slight devel- 
opment in media containing a small amount of acid, such as Liebig's 
meat extract. 

A feeble development was observed in sterilized hny infusion. 

The temperature range of the active multiplication of hog cholera 
bacteria lies between (Joo aiid 104c F,, being most favorable between 
85° and lOOo F. 

Hog cholera bacilli, though they seem to develop best in presence of 
oxygen, are capable of growing in what is practically a vacuum, *. e., 
they are facultative anaerobic organisms. Comparative experiments 
made with such obligatory aerobic organisms as bacillus subtilis deter- 
mined that while the latter shows no trace of growth in tubes from 
which the air has been removed, hog cholera bacilli grow quite as freely 
as in presence of air. When the latter are shaken up in liquid gelatine 
in test tubes and the gelatine rapidly congealed the colonies that appear 
throughout the gelatine show no difference in size, whether near the 
surface where air can penetrate or near the bottom of the tube. 

THE DIAGNOSIS OF IIOCI CHOLERA BY MEANS OF INOCULATION. 

The inoculation of small animals in the study of infectious diseases 
has been of the utmost importance from a diagnostic stund-point. Fre- 
quently bacteria which are nearly identical in form, size, and many 
biological characters, can only be distinguished from one another by 
their effect upon smaller animals. This is especially true of hog chol- 
era, since the specific bacillus closely resembles many forms found in 
decomposing liquids. In the following pages, therefore, a careful ex- 
position of hog cholera as manifested in small animals will be made to 
facilitate the diasrnosis of this disease. During the course of these in- 



70 

vestigatious rabbits have been fouud best for this purpose, altliongh 
ordinary bouse mice and guinea-pigs will answer almost as well. 

If a bit of spleen tissue from a case of bog cbolera be inserted under 
tbe skin of the tbigb, or simply rubbed upon a sligbt abrasion made 
on the inner surface of tbe ear, or if tbe bacilli from pure cultures be 
used, tbe disease will be induced. The rabbit will succumb within a 
period after inoculation varying from five to fourteen days (very 
rarely longer), depending upon the number of bacteria introduced. 
The period of incubation, during which the animal shows no symptoms, 
varies from three to five days before death. At this time the tempera- 
ture rises from the normal (102.oO-103.5o F., according to the age of 
the animal), to 107° or 108^ F.. and remains at that point unt'l shortly 
before death, when, if examined in time, a fall is observed. The height 
of the fever is accompanied by loss of appetite and a tendency to sit 
perfectly quiet. 

The disease thus induces in the rabbit a typical continuous fever in- 
variably ending in death. By way of illustration, the temperatures of 
a few cases are here reproduced : 

Kabbit inoculated June 18, with^ cubic centimeter culture liquid; 
weight, 2^ pounds ; temperature, 102.5° F. ; at end of first day, 102.7 ; 
of second day, 104.G; of third day, 105; of fourth day, 108; of fifth 
day, 10G.4: ; dead on sixth day. 

Eabbit inoculated June 20, with infected soil, one and one-half 
months old; temperature on fifth day, 10.'i.4 ; on seventh day, 103.8; 
on eighth day, 103.8; on tenth day, 107.fi; on eleventli day, 107.4; dead 
on twelfth day. 

Rabbit inoculated June 28, with i cubic centimeter of culture liquid ; 
weight, 2yg pounds; temperature, 103.7° F. ; end of first day, 103.3; 
of second day, 105.5; of fourth day, 107.8; found dead on seventii 
day. 

The lesions produced are very constant and characteristic. At the 
point of inoculation there is a slight infiltration of the subcutis and 
fascia, and occasionally a slight superficial necrosis of the muscular tis- 
sue. The spleen is very large, perhaps t hree to five times its normal size. 
The liver presents on its surface yellowish white patches which corre- 
spond to one or more lobules which have undergone coagulation necro- 
sis. These patches vary greatly in number but are rarely absent, pro- 
vided the animal lived long enough to permit their formation, i. e., not 
less than seven to eight days after inoculation. 

This necrosis appears chiefly in lobules near the surface, although 
occasionally the entire tissue is involved. In some livers the necrosis 
is complete so far as the lobule is concerned. In others it is restricted 
to the peripheral or portal zone of the lobule, in which case a large 
patch of lobules usually undergo the same change. There can be no 
doubt that they represent dift'erent stages in the process which seems 
to begin in the portal area. When sections are examined under the mi- 
croscope the liver-cells show as unstained nmsses without nuclei. There 



71 

is a remarkable absence of leucocyte infjltration aroniul the necrosed 
tissue. The bacilli are very well brought out in such tissues after thor- 
ough hardening in alcohol, by staining over night in aniline water 
methyl violet (tubercle stain), and decolorizing slightly in A to 1 per 
cent, of acetic acid. The deep bine bacilli a])pear in dense masses, 
chiefly in the capillaries along the edge of the necrosed area. The ne- 
crosis is most probably due to the plugging of the different vessels, 
thus cutting off the blood supply. 

The enlargement of the spleen and the necrosis in the liver are the 
two important characters of the inoculation disease. In a moderate 
number the intestinal tract is found diseased. The submucosa of the 
duodenum near the pylorus is dotted with ecchymoses, which may fuse 
into a single hemorrhagic patch. Besides this the submucosa of the 
large intestine 2 to 3 inches from the rectum, i.e., the straight portion 
merging into the rectum, may be iu the same condition. Sometimes the 
nuicosa is beset with minute bulging ha'matomata. These intestinal 
lesions are due to the discharge of bacilli from the necrotic foci in the 
liver into the bile ducts aud thence into the duodenum. The lesions in 
the large intestines may be influenced by the more or less prolonged 
stay of the feces before final discharge. 

In some cases when the disease has lasted from ten to thirteen days 
there is a peculiar exudate iu the large intestine, which may be drawn 
out of the anus in the form of bands or cylindrical masses ] or 2 feet 
long, consisting of a translucent, elastic, whitish material, finely fibrd 
lated when examined under a high power. The duodenum may be dis- 
tended with a straw-colored semi-gelatinous mass. Hemorrhagic lesions 
may also be present. It seems very probable that the exudate is the 
result of a fibrinous or croupous inflammation of the large intestine due 
to the presence of hog cholera bacilli. 

The lungs are occasionally the seat of hemorrhages. The kidneys 
contain more blood than usual, but hemorrhages are absent. Hog chol 
era bacilli are obtained by cultivation from uearl\' all the internal organs. 
They are usually so abundant in spleen aud liver as to be detected 
readily iu cover-glass preparations. 

The following experiment shows how few bacteria are required to pro- 
duce the divsease : 



Rabbit Ko.^;i^-l-itV Remarks. 



17 1 oBii'jjBis c. c Dead on sixth day. 

18 iBBOBij c. c Dead on ninth day. 

19 1 4500OB5 c. c Dead on eighteenth day. 

20 I jgnJsiyTj c. c Dead on eighth day. 



The beef-infusion culture was diluted so that one-quarter of a cubic 
centimeter of the liquid contained the equivalent given in the table. It 
s probable that ^o. 19 took the disease from No. 20, penned with it. 
The latter had ecchymoses iu the duodenum, indicating that the bacilli 



72 

bad escaped into the intestinal canal and were being discharged with 
the feces. The time of death of Xo. 1.9 suggests this view. 

A very small number of bacilli, therefore, are sufticient to produce in 
rabbits an infectious fever, or septiciiemia. 

The characteristic action of hog cholera bacteria on the mucous mem- 
brane is well illustrated by feeding cultures to rabbits: 

kSeptemljer 11, 1888. — Two rabbits were starved for one day and then 
fed hog cholera bacilli from an agar culture on clover. This was readily 
consumed. 

One rabbit was found dead on the sixth day. Agglutination of blad 
der to cajcum ; serosa of stomach reddened. Ileum about G inches from 
valve invaginated for 2 to 3 inches. Spleen congested, slightly en- 
larged. Liver and kidneys engorged. Large numbers of hog cholera 
bai.'illi in spleen, as tested by the microscope and cultivation on gela- 
tine. The other rabbit died in thirteen days. Spleen very large, con- 
gested ; coagulation necrosis in liver. Lungs contained several dark- 
led hepatized areas. Severe lesions were found in the large intestine. 
The mucous membrane of lower colon and rectum were dotted with 
small bulging hemorrhages, and the tube contained a cylindrical mass 
of a material resembling colorless gelatine, partially softened in water 
and very elastic (tibrin?). Tiie duodenum was distended with a pale 
yellowish translucent semi-gelatinous mass. Hog cholera bacilli as 
above. 

At the same time two other rabbits were starved for a da>' and then 
5 cubic centimeters of a liquid culture was added to 20 cubic centime- 
ters wati-r and given them to drink. One rabbit died in ten days. The 
lesions were the same as those in the rabbit just described, with this 
exception, that there was no coagulation necrosis in the liver. The 
other rabbit did not take the disease. It is quite likely that it may 
not have taken much of the water. 

When rabbits are not easily procurable the ordinary house mice may 
be used. They usually appear quite well and active after inoculation 
until some morning they are found dead. The period of the disease is 
the same as that for rabbits. The spleeu is very large; the liver con- 
tains many centers of necrosis. Mice have been frequently fed both 
with pure liquid cultures and with spleeu pulp containing hog cholera 
bacilli. They invariably take the disease and die within seven or eight 
days after the first feeding, with lesions the same as those observed in 
mice inoculated subcutaneously. Two mice were peculiarly affected the 
day after eating some spleen pulp. They were scarcely able to move. 
Their limbs sprawled, and on being taken out of the jars they remained 
in this position unable to escape. They died subsequently of true in- 
fection. The symtoms recorded were due very likely to the absorption 
of the ptomaine produced hj the bacteria in the digestive tract. 

There is a remarkable regularity in the length of the disease in mice. 
Those inoculated at the same time and with approximately the same 
dose usually die not more than a half a day apart; they appear lively up 
to the night during which they die. In one case four mice, inoculated 
at the same time, all died in the night of the seventh day, though they 
appeared well the day previous. 



73 

The followiug- experimeut is wortb}' of record as iudicatiug the effect 
of hog cholera virus on mice that survived infection : 

October 28, 1S8S. — Two mice were fed witli bits of liver and kidney 
tissue from mice whicli liad succumbed to inoculation with hog cholera 
cultures. The material fed had been kept in the refrigerator Hoc nearly 
four weeks in salt solution. Before feeding it was thoroughly mixed 
with bread crumbs and placed in the mouse cage. Both mice survived 
the feetliug and were active December 1, over one mouth after feeding. 
One was thereupon killed with chloroform and examined. The spleen 
was very much enlarged, not congested abnormally. On the ventral 
aspect of the liver a whitish patch where diaphragm was adherent. 
Under the patch a large abscess. This, was without doubt the site of 
extensive coagulation necrosis, which was now broken down. 

The second mouse was killed December 19. over seven weeks after 
being fed. The spleen was likewise very large, the liver intact, but 
there were live abscesses in the left kidney, with adhesions to .surround- 
ing structures. On section one abscess was wedge-shaped, tlie apex 
being at the pelvis; the whole only partlj^ softened. These also were 
the result of coagulation necrosis. We have here a striking illustration 
of the mainly mechanical injur,y doue by hog cholera bacilli. 

The effect of hog cholera bacilli on guinea-pigs differs but little from 
that exerted on rabbits and mice. The duration of the disease and the 
lesions are the same. There seems to be a somewhat greater tolerance 
in guinea-pigs, although the small number used does not justify any 
decided statement. 

Pigeons arc also susceptible to this disease, but by no means to the 
degree witnessed in the animals just mentioned. It requires about 
three-fourths of a cubic centimeter of an ordinar^^ beef infusion pep- 
tone culture to produce a fatal result (/. e., about 150,000 to 3,000,000 
times the dose necessary to destroy rabbits). The birds frequently 
died within twenty-four hours after the injection, which was usually 
made under the skin over the pectorals on one or both sides. The 
pectoral after death is x)artly or wholly discolored, and has a par- 
boiled appearance. The injected bacteria are present in the heart's 
blood and in other organs, notably the liver. If the dose is smaller 
than three-fourths of a cubic centimeter, the bird may survive after 
a week or two of pronounced illness. A large sequestrum forms in 
the pectoral muscle, which is gradually absorbed. Occasionally the 
birds will die after a week of illness manifested by diarrhea, ruffling 
of the feathers, and a quiet, somnolent attitude in a corner of the 
cage. Hog cholera bacilli are also present in the internal organs in 
such cases. Feeding cultures has no effect. 

Fowls have been frequently inoculated and fed with cultures without 
showing any signs of susceptibility. Among other animals inoculated 
were several white rats, one gray rat, one sheep, and a calf. lu none 
did the disease appear. In the sheep and calf a small abscess was 
found at the place of inoculation. 



VITALITY OF HOG CHOLERA BACILLI, AXD THEIR RESISTANCE 
TO VARIOLS DESTRLCTH E AGENTS. 



The vitality of bog cliolera bacilli in cultures remains for months nn- 
chauged. The following is perhaps an extreme illustration : 

A tube of beefs blood serum, coagulated by lieat, was inoculated with 
hog cholera bacilli November 28, i885. The platinum wire penetrated 
the blood serum and the bacteria grew as a slender i)lug in the needle- 
track and as a thin film on the surface. In July, 1887, more tlian one 
and one-half years later, a tube of beef infusion inoculated from the blood 
serum culture became promptly turbid, and contained the hog cholera 
bacilli only. Two mice inoculated subcutaueously with a few drops 
August 2, died Augusts and 9, respectively, with lesions characteris- 
tic of the disease and with the bacilli present in spleen anvl liver. The 
germs had not therefore lost their virulence. The blood serum had con- 
tracted but slightly from loss of water, there being very little evai)o- 
ration from the culture tubes used. 

Resistance of hog cholera hacieria to heat in liqnids. — A knowledge of 
the degree of heat necessary to destroy liog cholera bacteria is of con- 
siderable importance, not onlj" in its bearing upon the ap[)lication of 
heat as a disinfectant, but also upon the various processes that are used 
in the preparation of pork for consumption. 

Culture tubes containing about 10 cubic centimeters of beef infusion 
were inoculated from a culture of a certain age and then placed in a 
water-bath kept at the desired temperature. They were exposed for 
different periods of time and then removed to an incubator at 95° F. 
When the tubes remained clear it was inferred that the bacteria had 
been destroyed. A control tube was inoculated in every experiment 
to make sure of the vitality of the culture used. 

A momentary exposure to boiling water will destroy them. When 
the temperature of the surrounding water is 158° F. (7(P C). the in- 
oculated tubes remain sterile after an exposure of four to five minutes. 
As it takes about four minutes for the temperature of the culture liquid 
to reach 70° C, it is probable that a two minute^' exposure to 70° C. 
would be sufficient. 

An exposure to 130° to 138° F. (58°-59° C), is sufficient to destroy 
hog cholera bacteria in fifteen minutes. The same is true for bacteria 
taken directly from the spleen. An exposure to 130° F. (54.5° C.) will 
destroy them in one hour. Tubes exposed for one-quarter of an hour 
become turbid within twenty-four hours. Those exposed for one-half 



76 

and three-quarters of an hour become turbid within fort^-eight hours. 
This shows that most of the bacteria have beeu destroyed by such pro- 
longed exposure. Tubes heated for one hour remain clear. 

When the temperature is still more reduced, to 120^ F. (49^ C), ex- 
posure for a period as long as two hours is insufiicient to destroj^ them, 
altliough their growth may be slightly retarded. 

It must be remembered that these results mean that the bacteria 
must be actually exposed to these temperatuies for the length of time 
indicated. In the culture tubes employed it takes about five minutes 
to bring the temperature of the liquid up to 70° C, and less for lower 
temperatures. If, therefore, it takes longer than this for tiie heat to 
penetrate into meat or lard containing these bacteria, their destruction 
can not be regarded as certain within the time indicated above, and 
the exposure to the required temperature must be correspondingly 
lengthened. 



Hog cliolera bacteria in 10 cubic centimeters bouillon placed in a water-bath at — 



1C0°C. (212° F.).. 
70° C. (158° F.)... 
58° C. (138<^F.)... 
54.50 c. (ISO'^^F.). 
49° C. (120° F.)... 



Time in which 
.destroyed. 



Immediately. 
4 minutes. 
15 minutes. 
1 hour. 
Not in 2 hours. 



Bacteria do not so readily succumb to heat when dried and then ex- 
posed to dry hot air. It was found that dry heat at 80° C. (170° F.) is 
sufficient to destroy the bacteria when exposed in a dry state for fifteen 
minutes. 

In these experiments bacteria from cultures were rubbed on the inner 
side of plugged and sterilized test tubes. Gelatine was added after they 
had been exposed to the heat and roll cultures made. Absence of growth 
indicated the death of the contained bacteria. 

Kesistance to freezing is well illustrated in the experiments reported 
in the section on the vitality of hog cholera bacilli in the soil during 
winter. 

Vitality of hog clioUra bacteria in ordinary water. — The hardiness of 
this microbe is well illustrated by its capacity for multiplication in or- 
dinary drinking water. To determine this, the following experiment 
was made : 

September 8, a culture tube containing very clear Potomac drinking 
water* which had been sterilized several weeks previous by a tem- 
perature above 110° C, was inoculated with a platinum loop from a 
pure liquid culture of the bacillus. By mixing a given quantity of this 
water immediately after inoculation with gelatine, and making a plate 
culture of the same, it was found that the water contained about 20,240 

* When drawn this water did not contain more than 100 to 200 bacteria to the cu- 
bic centimeter. 



77 

bacteria in 1. cubic centimeter. The water was kept in the laboratory, 
in wbicli the temperature corresponded closely ^ith that prevailing out- 
doors. It was examined from time to time on gelatine plates, and the 
number calculated for 1 cubic centimeter. The following figures give 
the results obtained : 

September 8, 2G,'-'J:0 in 1 cubic centimeter (immediately after inocula- 
tion). 

September 9, 201,<)()0 in 1 cubic centimeter. 

September 10, 1,290,000 in 1 cubic centimeter. 

September 11, too numerous on plate to be counted. 

September 13, 2,008,200 in 1 cubic centimeter. 

September 15, 1,519,500 in 1 cubic centimeter. 

September 17, ],.3()0,308 in 1 cubic centimeter, 

September 29, 83,700 in 1 cubic centimeter. 

October 12, 19,125 in 1 cubic centimeter. 

October 21, 10^880 in 1 cubic centimeter. 

November 18, 225 in 1 cubic centimeter. 

December C, a few bacteria still present, as determined b,y liquid cult- 
ures. 

January 4, 17 in 1 cubic centimeter. 

January 11, no growth on plates. 

According to another experiment the vitality lasted about two 
months. 

June 13, 18S8, 30 cubic centimeters, Potomac drinking water, sterilized 
in a Salmon culture tube, was inoculated with a platinum wire to whicli 
a minute bit from the surface growth of an aijar-agar culture adhered. 
Plate cultures prepared immediately after thoroughly shaking the tube, 
indicated that each cubic centimeter of the water contained from 
1,000,000 to 2,000,000 germs. 

Plate culture of June 14 shows in Jg cubic centimeter of water a very 
large number of colonies. Roll cultures made June 22, July 3, and July 
16 contain a smaller number. 

A roll culture of August 4 contains about 200 colonies {i. e., about 
0,000 in 1 cubic centimeter). 

A roll culture of August 25 remains sterile. A tube of beef infusion 
to which about 1 cubic centimeter of the water had been added Sep- 
tember 15 contained a large coccus five days later; no hog cholera 
germs. 

These cultures show that the bacilli perished in about two months. 
The difference in the results obtained in this and the last experiment 
may have been due to the season of the year. 

That the bacilli can be kept alive in clear river water for from two to 
four months and perhaps longer is a fact very significant in itself. When 
we consider, moreover, that the added bacteria in the first experiment 
multiplied so that each individual was represented by ten at the end of 
five days, the hardiness of the bacillus is very evident. The danger 
from infected streams into which feces from sick animals find their way 
is thus proved beyond a doubt. Stagnant streams and pools are more 
dangerous, since the water is but slowly renewed, while in rapidly flow- 
ing streams the bacteria are speedily carried away. On the other hand, 
the latter may spread an epidemic from one place to another. 



78 

Besistanre to continuous drying at ordinary temperature (60° to 80° F. — 
A number of experiments were made to determine this point. Some of 
tbem are reported in full in preceding Annual Reports of the Bureau, 
and are therefore simpl3' summarized in this place. 

(1) A series of cover-glasses, upon each of which a drop from a liquid 
culture had been dried, were placed in bouillon at dift'erent times. No 
growth in bouillon after they had been dried from seven to nine days. 

(2) Minute bits of spleen tissue from a pig which had succumbed to 
hog cholera were tlried on cover-glasses. These were capable of infect 
ing bouillon uj) to the twenty-third day. 

(3) Spleen tissue dried on four cover-glasses gave rise to pure cult- 
ures of hog cholera bacilli after forty-nine days. 

(4) Hog cholera bacteria from a liquid culture one week old, dried on 
silk threads, were placed on a gelatine plate from time to time to ob- 
serve any growth. They were stilfcapable of develoi)ment after tweury- 
one days, when the stock of threads was exhausted. 

^^5) Threads steeped in a liquid culture one day old and dried were 
placed on gelatine plates, as described in series 4. No colonies ap- 
peared on the twenty-seventh and twenty-eighth days. A few appeared 
later on, showing that even after thirty days a few still survived. 

In these series of experiments the vitality of the bacilli was not ex- 
hausted after forty-nine days in one series; in another it was destroyed 
in less than ten days. 

The following series of experiments, made during the i)resent year, 
show how very varied is the length ot time during which the bacilli 
remain alive when dried: 

June 15. — Minute bits of spleen tissue, from a rabbit whicli had died of 
hog cholera after inoculation with a pure culture, were rubbed on sterile 
cover-glasses and kept under a tlamed funnel, plugged with cotton- 
wool. 

On July 3, G, and 9 two cultures were made by dropping into each 
tube of beef infusion a cover-glass. All six tubes remained clear. The 
bacilli had thus perished within three weeks. 

In the following experiment hog cholera bacilli remained alive for 
more than four months: 

June S. — From an agar-agar culture, three days old, some of the 
abundant surface growth was placed upon sterile cover-glasses, each 
receiving about as much as the point of a platinum wire could hold. 
These were placed on a flamed glass support under a flamed and plugged 
glass funnel, and kept in the laboratory, the air of which was moderately 

dry. 

Two cover- glasses droi)ped into beef infusion pei)tone June 25. One 
culture remains clear, the other clouded in one day ; contained only n)o- 
tile hog cholera bacilli. 

Two covers were added to beef infusion June 20, July 0, and July 
16. All six cultures became clouded and contained only hog cholera 
bacilli. 

Of two cultures made July 23 only one becomes clouded, and is a 
pure culture of hog cholera bacilli. Of two cultures made August 2, 
both become clouded with liOg cholera bacilli only. 



79 

Four cultures, made on August 0, 22, 30, aud September 14, became 
clouded with tlie same microbes, aud these alone. A tube into which a 
cover-glass bad been dropped September 21 remained sterile. A tube 
inoculated in the same way September 26, became turbid on the second 
day, and contained hog cholera bacilli only. A tube inoculated on Oc- 
tober 8 was still fertile. The stock of cover glasses had become ex- 
hausted. 

It will be seen from the above results that some of the germs were 
dead in one and a half and three and a half months; all the rest were 
capable of multiplication for four months. The prolonged vitality was 
no doubt due to the massing together of the germs from the OQar cul- 
ture, for on those cover glasses which failed to inoculate cultures, or in 
which the appearance of growth was retarded, the quantity of growth 
was smallest. The interesting question here arises whether it is the 
oxygen of the air which gradually destroys the bacilli, since this is more 
or less kept away when they are massed together, and since all pre- 
vious experiments with bacilli suspended in liquids have shown that 
the period of their vitality may average not more than two months 
when in a dry condition. 

On August 30, after having been dried for two months and twenty- 
two days, two mice Avere inoculated with a liquid culture obtained from 
one of the cover-glasses. Both died of hog cholera on September 14 
and 15, respectively. 

The vitality of hog cholera bacilli during continuous desiccation may 
thus last from two weeks to more than four months. 

In the soil, and in nature generally, bacteria are rarely subjected to 
continuous drying, but to alternate wetting and drying. In order to 
observe the effect of such alternation, some of the same agar-agar culture 
used in the preceding experiment was placed in the bottom of a sterile 
watch glass under a funnel June 8. 

June 15. — About one-third cubic centimeter of sterilized distilled 
water added to the* watch-glass, so as to cover the dried film completely. 
The water was evaporated entirely next day. 

June 22. — Sterile water added again ; dried up next day. 

July 3. — Water added again aud two cultures made; both remain 
sterile. 

July G. — A liquid culture made by adding some sterile water to the 
dried culture mass, stirring it up aud transferring the water with a sterile 
pipette to a tube of beef infusion. This also remained clear. 

Thus bacilli from the same culture which resisted continuous drying 
for at least four months were destroyed in less than a mouth when a 
moist and a dry state alternated. This fact, so striking aud important, 
needed confirmation. 

September lij. — A considerable quantity of the surface growth from 
an agar-agar culture two days old was rubbed on the bottom of a sterile 
watch-glass covered by a plugged funnel as before. Thoroughly dry 
next day. 

September 18. — A small quantity of sterile distilled water added. This 
was dried up next day ; the germs had spreacl out into a thin layer. 



80 

September 21. — Sterile water added agaiu and a tube of beef infusion 
peptone inoculated with a loop from tlie liquid stirred u[>. Tube turbid 
with lioj;' cholera bacilli next day. 

September 20. — Sterile water added again. The tube of beef infusion 
peptone inoculated at the same time. Pure culture next day. 

October 1. — Tbe same process repeated ; culture contains hog cholera 
bacteria. 

October 8. — Dried bacilli wetted again with sterile water. Tbe cul- 
ture made from them becomes turbid; only hog cholera bacilli present. 

October 15. — The same i)rocess repeated; the inoculated tube be- 
comes turbid after forty-eight hours. 

October 22. — After wetting the dried growth again, it was thoroughly 
stirred up and several drops added to a liquid culture. This tube re- 
mained permanently clear. 

This experiment therefore confirms the other in showing that hog 
cholera virus is far more quickly destroyed when it is alternately mois- 
tened and dried than when it remains continuously dry. In both tests 
the germs died in one-third the time required to destroy dried virus. 

SOME EXPERIMENTS ON THE LENGTH OF TIME DURING WHICH HOG 
CHOLERA VIRUS REMAINS ALIVE IN THE SOIL. 

The virus of hog cholera is quite tenacious of life in spite of the fact 
that no spores are foruied. During the past year some preliminary 
experiments were made concerning the vitality of hog cholera bacteria 
in the soil. This becomes infected during epizootics of this disease by 
the discharges of the sick perhaps more thoroughly than anything else 
in the surroundings of the animals. Moreover, it is the most difficult 
to disinfect, as we have no knowledge of the depths to which the living 
virus may be carried by water. If it can be shown that the life of such 
virus in the soil is speedily destroyed, the piecantions to be taken would 
be quite different from those needed if it exists for a long period of 
time. 

Experiment 1.— A small flowerpot containing soil was sterilized by 
moist heat at 110° to 118° C, and protected from drying and dust by a 
large bell jar. On its surface about 100 cubic centimeters of a bouillon 
peptone culture of hog cholera bacteria was poured and the whole main- 
tained moist and at thelaboratory temperature. The soil used was a very 
fine loam from thegrounds of the Department of Agriculture. The bulk 
of the soil consisted of grains not larger than j-,\^ milliuieter (..^^^g iuch). 
Eoll cultures from the soil after a few days demonstrated the presence 
of immense numbers of bacteria. From this soil rabbits were inocu- 
lated from time to time by stirring up a little soil in some sterile beef 
infusion and injecting the clear supernatant li(iuid hypodermically. The 
soil was infected September 17, 1887. The appended table gives 
the inoculations into rabbits to test the virulence of the soil. The rab- 
bits which succumbed died of hog cholera, as indicated by the lesions 
and the bacteriological examination, 



81 



No. 


Date of 
inocu- 
lation. 


Time after in- 
fection of soil. 


Died. 


Kemai'ks. 


1 


Oct. 10 

Oct. 18 
Nov. 4 
Dec. 12 

Jan. 9 
Jan. 23 


Mos. Days. 
23 

31 
40 

2 2.3 

3 23 
3 23 


Oct. 17 


Enlargement of spleen ; coagulation-necrosis in 
liver; hemorrhagic lesions in duodenum and 
rectum, in lungs and heart; numerous hog 
cholera bacteria in spleen and liver. 

Spleen and liver and lungs as in No. 1. 

Spleen, liver, duodenum, and rectum as in No. 1. 

Spleen large, pale; coagulation-necrosis in liver 
slight ; no other lesions ; hog cholera bacteria 
as in No, 1. 


3 


Oct. 24 

Nov. 12 


4 


Dec- 23 


6 


Eeniains Tvell 

...do 













The infectious quality of tliis soil wheii a mouth old was tested on 
two pigs, by feediug each directly with a tablespoouful of the soil. One 
showed no disease; the second, a young i^ig, became very sick and was 
killed on the eighteenth day, being unable to rise. 

A utopsij. — Animal about eight weeks old, very thin. No skin lesions. 
Lungs normal, excepting the cephalic and ventral lobes of left lung, the 
ventral and the root of principal lobe of right lung. These are airless, 
bright red, mottled with yellowish points, indicating broncho-pneu- 
monia. The spleen was small. The lymphatic glands of large intestine 
very large, tough, whitish. The walls of caecum and colon over one- 
eighth inch thick; do not collapse when slit open. The mucosa is 
everywhere covered by a lirmly adherent yellowish-white slough, ex- 
tending as far as rectum. The ileum for about 2 feet from lower end 
has the mucosa likewise involved in superficial necrosis, but only on 
the summit of the longitudinal folds. In the stomach a portion of the 
fundus is covered by a friable deposit made up chiefly of large granular 
cells with single nucleus. Gelatine and liquid cultures from heart's 
blood and spleen contain only hog cholera bacteria. The gelatine cult- 
ures indicate only a moderate number of colonies. The bacteria had 
also penetrated into the diseased lung tissue. They were obtained on 
plate cultures, and a rabbit inoculated subcutaueously with some beef 
infusion in which a bit of lung tissue had been torn up died in eleven 
days with coagulation necrosis in liver, enlarged spleen, and numerous 
hog cholera bacteria in both organs. The broncho-pneumonia may 
have been due to the aspiration of some of the soil during the forced 
feeding. 

It has thus been shown that moist soil, not allowed to dry out and 
kept in a summer temperature ranging from G0° to 05° F., retained its 
virulence for rabbits from two to three months. At the end of this 
time fungi and other bacteria had found their way into the pot of soil? 
as shown in roll cultures. This and other reasons drawn from observa- 
tions of this germ lead to the conclusion that its life becomes extin- 
guished with its pathogenic effect on rabbits. This phase of the ques- 
tion is not to be overlooked, for even if a germ should no longer prove 
pathogenic, but remain alive, it is not improbable that it may regain its 
original virulence under certain unknown circumstances. 
15612 H c 6 



82 

The severe disease caused iu the young pig with soil which had been 
iufected one month ago shows the great susceptibility of young animals 
to this disease. Since rabbits are most susceptible of any animals to 
hog cholera virus, it was not thought necessary to experiment on pigs 
after the former fiiiled to take the disease. 

It may be argued that the conditions of this experiment were abnor- 
mal, in that the bacteria were not exposed to the various meteorological 
conditions, such as rain and drought, freezing and thawing, and the 
competition with other bacteria in the soil. This is trne. The con- 
ditions just enumerated are opposed to such a long life in the soil. A 
condition favoring it, on the other hand, is the low temperature in winter, 
which may act as a means of preserving the life of bacteria. 

These objections were partially removed by the following experi- 
ments: 

Experiment 2. — A small pot, about 5 inches across the top, filled with 
soil, is placed in another pot of twice the diameter, also filled with soil 
in such way that the rims of both are on the same level. In this posi- 
tion they were sterilized for three and one-half hours, at a temperature 
of about 110<^ C, in a steam sterilizer. The outer pot was to protect 
the inner one to some extent from coming iu direct contact with the 
garden soil in which it was subsequent!}' placed. About 200 cubic cen- 
timeters of a beef infusion culture of hog cholera bacteria three days 
old was ultimately mixed with the soil of the inner pot by removing the 
upper layers and pouring the culture liquid upon the deep layers and 
then upon the surface, after replacing the superficial layers. The pots 
were then placed iu the grounds of the Agricultural Department so that 
the top was level with the surrounding soil. Nothing was placed over 
the surface to protect them from contamination with ordinary bacteria. 

The infected soil was placed in the grounds December IG, 1887 
During the remainder of December the outdoor temperature oscillated 
slightly above and below the freezing point, remaining for several days 
below this point at the end of the month. The soil in the pot was 
saturated with water during part of the winter and the surface covered 
with it. It had probably become tightly packed, and hence impervious 
after the culture liquid had been poured upon it. 

The appended table indicates the persistence in virulence of the in- 
fected soil as tested upon rabbits. The soil was taken from the surface 
of the pot, or from near the bottom as indicated, and the inoculations 
made as in the preceding experiments : 



83 



[Soil infected December 16, 1887.] 



Ko. 


Date of 

inocula- 

tiou. 


1 


Jan. 5 


2 


Feb. 1 


3 


Feb. 7 


4 


Fob. 2?, 


5 


Mar. 5 


6 


Mar. 21 



Soil taken 
from — 



Su'-face 

...do . 

Depth . 
SuifrtCt' 

..do . 
. . do . . 



Number of days 
afttn- iufoctiou 
of soil. 



Rabbit dies- 



20 days ranuary 10 . 



1 monili 13 days 

1 inoiith 19 days 

2 iiioiitlis 7 days 



Februaiy 18 



Marcb 5 



2 moutbs 18 days . Kemains well 

3 mouths o days . . 1 do 



Eomarka. 



Oiip lobe of liver involved in coaji- 
iilation-necrusis ; bacilli of boj; 
cholera present. 

Spleen very large, darli; coautila- 
tion-necrosis in liver; nuiuerous 
hoj; cholera bacilli in both oigauj. 

Killed Febrnary27; not diseased. 

Si)leen and liver as in No. 2; hem- 
orrhagic lesions in duoileniim 
and rectum; bog cholci-a bacilli 
present. 



Eabbit No. 3 was inoculated with soil from beneath the surface. This 
was obtained by removing- the inner pot, thmstiiii? a small metallic 
cork-borer previously tlame<l through the hole in the bottom of the pot 
upwards, about halfway to the surface. The soil brought down in the 
inside of the borer was used for inoculation. In this way it was ob- 
tained unmixed with soil from the superticial hiyer. The rabbit re 
mained well for twenty days after inoculation. This is longer than any 
period of incubation which wo have thus far observed. Owing to ex- 
tensive disease of the external ear caused by psoroptes (lice), it was 
killed on the twentieth day. There *vere no indications of liog cholera. 
The deeper layers of the soil had thus rid themselves of the infectious 
material sooner than the surface. EoU cultures showed the presence 
of a large number of pearly colonies s])rending rapidly and made up of 
non-motile bacilli. 

Kabbit No. 2 lived seventeen days after inoculation. Was tliis long- 
period of incubation due to an attenuation of the virus, or to the scar- 
city of the surviving- bacteria? The lesions were practically identical 
with those usually found. In order to learn whether attenuation had 
actually taken place, a rabbit was inoculated subcutaneously with three 
to four drops of a beef infusion culture prepared from the blood of No, 
2. It died in five days with extensive coagulation-necrosis in liver; 
spleen very much tumefied and petecchiiB in rectum. There was no at- 
tenuation, therefore, so far as the second rabbit is concerned. There 
still remains the possibility that the bacteria, attenuated when inocu- 
lated into the first rabbit, grew in virulence during the long i)eriod of 
incubation until tliey had attained their original pathogenic power, 
when the rabbit died. 

Experiment 3. — February 2t>, two pots of soil, one within the other, 
were sterilized as in the preceding experiments. The soil of the inner 
pof. was saturated from below up with 100 cubic centimeters of a beef 
infusion culture one day old, of hog cholera bacteria. The whole was 
buried in the garden on a lev^el with the soil and not protected in 
9,ny way. Rabbits were inoculated with the soil as previously indicated . 



84 

[Soil infected February 20.1 



No. 


Date of 
inocula- 
tion. 


Soil talicn 
from— 


Number of 

days after 

inoculation. 


Eemarks. 


1 

2 
3 


Mar. 10 

Mar. 29 
..do.... 


Surface — 
Depth 


18 days 

38 days 

...do 


Eiibbit dies on eleventh day. Spleen very large ; coagula- 
tion necrosis in liver ; hog cholera bacilli present. 

Eabbit died on eighth day ; lesions as in No. 1. 











Soon after tlie last inoculation the pot of soil was accidentally re- 
moved by laborers working in the garden, so that tbe experiment came 
to a premature close. It shows, however, that the bacteria in the depths 
of the soil were alive thirty-eight days after iuoculation, while at this 
same time they were dead in the surface layers. 

Experiment 4. — Soil prepared, sterilized, and infected precisely as in 
the preceding exi)eriment, was buried in the garden April 4, 1888. The 
soil soon became packed hard and dry on the surface to a depth of one- 
half to 1 inch. The foUowiug table gives the inoculations: 

[Soil infected April 4.] 



No. 


Date of 
inocula- 
tion. 


After soil infection. 


Soil taken 
from — 


Remarks. 


1 

2 
3 


Apr. 25 

...do.... 
May 12 
...do 


21 days 

....do 

1 mouth 8 days 

.do 


Surface 

Depth 

Surface 

Depth 

- 

Surface 

Depth 

....do 

... do 


Dies April 30; enlarged spleen. Slight necrosis in 
liver. 

Dies May 2. Same lesions as in No. 1. 

Kemains alive. 

Dies May 21. Same as No. 1, besides hemorrhagic 
lesions in rectum. 

Kemains alive. 


5 
6 


May 29 
...do.... 
Juno 15 
...do.... 


1 month 25 days .. 
....do 


7 
fi 


2 months 11 days.. 
...do 


Dies June 29 ; spleen and liver lesions as in No. 4. 


9 

in 


July U 
...do .... 


3 months 10 days.. 
.. do 


....do 

do 


Do. 
Do. 







The presence of hog cholera bacteria was demonstrated by cultiva- 
tion from spleen and heart's blood in all the animals that died. 

Experiment 5. — Soil sterilized and infected with hog cholera bacteria 
as in preceding experinients. Placed in the department grounds Ma^^ 
18. June 20, surface layer dry and very hard ; boring necessary to get 
some of it out. Two rabbits inoculated from surface and deep soil. 
The result of these and subsequent inoculations is givou in the follow- 
ing table : 



85 

iSoil infected May 18. 1 



No. 


Date 
of inocu- 
lation. 


Length of time 
after soil infec- 
tion. 


Soil taken 
from— 


Ecniarks. 


1 


June 20 


33 daj-3 


Surface 

Depth 

Surface 

Depth 


Dead July 4 (hog cholera). 
Ueniains well. 

Do. 

Do. 


9 


do 


-do .. . 


3 
4 


July 20 
. . do .... 


2 months 2 days. . . 
....do 







Experiment 6. — July 14 a pot of soil was sterilized niul infected through- 
out with too cubic centimeters of a culture of hog cholera bacilli as 
before and placed in the Department grounds. 



No. 


Date of j Length of time 
inocula- 1 after soil infec- 
tion, tion. 


Soil taken 
from— 


Eemarks. 


1 


Aug. 10 

Aug. 10 
Aug. 24 
Aug. 24 


27 days 


Surface 

Depth 

Surface 

Depth .... 


Dies August 23! spleen very large. Necrosis in 
liver ; hog cholera bacilli in spleen ; intestines 
diseased. 

Died August 14 ; sjdeen and liver as in No. 1. 

Remains well. 

Do. 





... do 


3 
4 


1 month 10 days .. 
... do 



These various experiments extended over the coldest as well as the hot- 
test period of the year, and may therefore lay claim to more or less com- 
pleteness. They may all be brought together in the following table: 



No. 



Date of 
soil in- 
tcction. 



Sept. 17 
Dec. IG 
Feb. 20 
Apr. 4 
May 18 
July 14 



Rabbits failed to take the disease when inoculated — 



With surface soil after- 



3 months 23 days 

2 months 7 days 1 month 19 days 



Witli deeper soil after — 



1 month 7 daj's . . 

1 month 25 days . 

2 months 2 daj-s 
1 month 10 days . 



Not completed. 
3 months 10 days 
33 days. 
1 month 10 days. 



It may be said in general that hog-cholera germs will [)erish in the 
soil in from two to four months, dependingon the season, moisture, and 
depth from the surface. In what direction these three factors influence 
their vitality the experiments are not complete enough to show. We 
may, however, safel^^ assume that frost has no rapidly destructive effect 
upon tlieiu, while dryiug (experimeuts 5 and C) seems much more de- 
structive. Attention has already been called to the destructive effect 
of alternate wetting and drying. So far as the above results go, a pe- 
riod of at least four months should be allowed for the natural destruc- 
tion of hog cholera virus in the superficial laj^er of the soil, /. c, in 
a layer extending about 2 or 3 inches below the surface. 



86 

A FEW ADDITIONAL OBSERVATIONS AS TO THE VITALITY OF IlOa 
CHOLERA VIRUS IN THE SOIL AT THE EXPERIMENTAL STATION. 

(1) A pen has a coucrete floor, with agentlu slope towards the back. 
From January to December, 18SG, at least 70 pigs died in tliis pen from 
liog" cholera. During tliis time all the liquid in tlie pen drained into 
the field back of it. During February and March of 1887 a number of 
pigs in this pen died of swine plague. Two survivors from the disease 
were removed September 15, leaving the pen empty. In December, 
1887, the infected ground behind the pen was inclosed, making a yard 
G feet deep and IG feet long and communicating with tlie i)ei]. Decem- 
ber 15, 1887, 3 pigs about two months old were placed in the concrete 
])en and allowed to run in the yard behind it. All three continued 
well. To make sure that there were no ulcerations escaping observa- 
tion one of the pigs was killed one and a half months after their trans- 
fer to this pen. There were no lesions indicative of hog cholera ; cult- 
ures from the spleen remained sterile. The two remaining pigs were 
well three and a half months later. 

These observations show that ground thoroughly infected for more 
than a year was free from infectious properties eight moiitiis after the 
death of the last case. 

(2) Upon a plot of ground of one-fourth to one-third aero about 100 
pigs which had died of cholera during 188G were buried, being covered 
with li to 2 feet of soil. During 1887 no animals were buried here, but 
many had been interred within 3 to 8 rods of this plot during the latter 
half of the present year. A triangular yard 16 feet on each side was 
fenced off upon the old ground, with a movable pen in. one corner for 
shelter, 

December 15, 1887, 3 pigs were penned in this yard. They remained 
well ; one and a half months later 1 was killed and found healthy. 
The two remaining ones were well after three and a half months. 

This experiment shows that ground containing the bodies of numer- 
ous aiiimals which had died of hog cholera wi^s not infectious after one 
year. 

(3) The following notes are valuable in illustrating how rapidly the 
ground may be freed of infectious matter : 

A yard 6 by 10 feet was enclosed by a fcm-c and made to communicate 
with a double pr-n having concrete floors. This pen had been infected 
by pigs from the outbreak described on page 37. The soil of the yard 
is a clay loam. 

]S\)vemhcr 27. — Nos. 434, 435 now occupy the i)cn and Nos. 4oG, 137 
added to day. 

November 28. — Nos. 434, 435 both die of hog cholera. These had been 
infected by feeding (see p. 50 for notes on these and other animals in 
this pen). 

December 10.— Viscera fiom i^o. 42 fed to Nos. 43G, 437. 

December 12. — Viscera from No. 43 scattered over the soil of the yard, 



87 

readily eaten by Nos. 4oG, 437 ; later in the day :N"os. 439, 440, and 443 
added. 

December 17. — Viscera from l^o. 47 and No. 48 scattered over the 
ground, and Xos. 448 to 453 inclusive placed iu the yard. 

December 27. — No. 443 dies of cholera. 

December 28. — No. 448 dies of acute cholera. 

December 29. -Nos. 43G, 439, 440, 149, and 452 all die of acute cholera. 
The pen may now be said to bo thoroughly infected. 

Januarij 1, 1888. — No. 437 found dead. 

January 3. — Nos. 450, 451, and 453 removed. 

Januarif 10. — After the yard and pen have been vacant for a week 
and simply brushed out but not disinfected nor cleaned thoroughly 
two healthy pigs (Nos. 479, 480) are placed in it to determine whether 
the ground is still capable of giving the disease. 

During the greater part of January the ground was frozen over, but 
during l^'ebruary and March there are frequent, i)rolonged thaws. 

March 29. — Nos. 479, 480 have remained well since January 10. They 
are now removed. The yard itself is now converted into a genuine 
mud-hole. 

March 30. — Two fresh pigs are transferred to tiiis yard. 

July 24. — They have remained well for nearly four months. 

This virus was in the first place either destroyed or made harmless 
by the prolonged frosts iu January, so that the pen and yard were 
thoroughly disinfected by natural agencies and perfectly safe two months 
later. The disease did not reappear in the following midsummer. It 
may also be seen from the notes that the two i)igs placed in the in- 
fected pen but one week after the removal of diseased and infected ani- 
mals did not take the disease, perhaps because the infectious matter 
was frozen up and slowly killed in this condition before they could get 
at it. 

THE EFFECT OF SOME DISINFECTANTS ON THE VIRUS OF HOG 

CHOLERA. 

In the report for 18SC there are given in extenso a series of experiments 
to test the destructive power of the more reliable disinfectants on hog 
cholera bacilli from liquid cultures usuallj' from one to two days old. The 
results, owing to their practical importance, are also summarized here. 

The method employed needs a few comments. A few drops of cult- 
ure liquid were added to the disinfectaut solution in a sterilized watch 
glass under a bell glass. After certain regular intervals of time plati- 
num loops holding about y^^ cubic centimeter were used to transfer 
this liquid to tubes of beef infusion. These were placed into a ther- 
mostat and watched for a number of days. The loop of disinfectant 
carried over into 10 cubic centimeters of sterile beef infusion is diluted 
to such an extent (about 1,000 times) as to be practically of no account 
whatever. This method is more sensitive than the method originally 
employed by Koch. He used bits of silk thread impregnated with the 
specific organism to be tested and placed them upon plates of gelatine 
to develop. 



88 

It has been suggested that hog cholera bacteria may survive in the 
brine from salted meats long enough to be exported to other countries 
and communicate the Tiisease. It need not be said that this is impos- 
sible, for the attenuating action of a concentrated salt solution would be 
in itself sufficient to speedily destroy the pathogenic power of the bacilli, 
even if their life were not destroyed. The following experiment shows, 
however, that they are absolutely killed within four weeks : 

Ten cubic centimeters of a saturated solution of common salt was 
added to each of three culture tubes. These were then sterilized and 
1 cubic centimeter of a fresh bouillon culture of hog cholera bacilli 
mixed with the contents of each tube. Small quantities of liquid from 
one of these tubes were introduced into sterile bouillon every two or 
three days. Up to the twenty-first day the bouillon became clouded, 
indicating that the bacilli were still alive in the brine. After the 
twenty-ninth day the bouillon remained clear. The two remaining 
tubes of brine hitherto untouched were also found sterile when exam- 
ined by means of cultivation a day or two later. 

Mercuric chloride was found destructive to the bacillus when diluted 
in the proportion of 1 : 75000 (.001^ per cent.). 

Several drops of a culture were mixed with about 1 cubic centimeter 
of a .1 per cent, solution, and tubes inoculated from this at the end of 
two, four, six, eight, and ten minutes. Tubes remain sterile. To show 
that the antiseptic efl'ect of the liquid transferred with tbe platinum 
loop was nil, one of these tubes was inoculated again from another cul- 
ture. This tube was turbid on the following day. 

Five tubes treated in the same way with .05 per cent, solution. All 
remain sterile. 

Five tubes inoculated with bacteria exposed for the same periods of 
time to a .01 per cent, solution. All remain clear. 

Five tubes treated as before, using a .005 percent, solution. Perma- 
nently clear. 

Five tubes treated as before, using a .002 per cent, solution. All 
tubes clear, excepting the one inoculated after six nnnutes' exposure. 

Five tubes inoculated at the end of five, ten, fifteen, twenty, twenty- 
five, and thirty minutes after exposure to a .001 percent. (1:100000). 
Tubes inoculated after five and ten minutes turbid next day. On the 
second day all but the one inoculated after thirty minutes turbid and 
containing pure cultures of the bacterium. 

The limit of disinfection for this period of time must therefore lie 
between 1 : 500000 and 1:100000; hence five tubes were inoculated as 
above, using a solution of 1 : 75000 at the end of seven, ten, fifteen, 
twenty, twenty- five, and thirty minutes. All tubes remained clear. 

Carbolic acid destroys the bacillus in solutions containing from 1 to 1^ 
per cent, of the acid by weight. 

Five tubes inoculated after treating bacilli from a liquid culture with 
a 1 per cent, solution for five, ten, fifteen, twenty, and twenty-five min- 
utes. All turbid on the following day. The two last tubes were also 
examined on gelatine plates and the cultures found pure. 

With a 2 per cent, solution five tubes inoculated after ten, fifteen, 
twenty, twenty-five, and thirty minutes remained sterile. The same 
result witn a li ])er cent, solution. With a 1;^ per cent., tubes inocu- 
lated at the end of seven, ten, fifteen, twenty, twenty-five, and thirty 
minutes remained clear, excepting the first, which contained bacillus 
siibtilis. 



89 

Passings to a one-half percent, solntion, tubes inoculated at the same 
intervals became turbid with the bacterium sown. With a three-fourths 
per cent, solution the result was the same. 

Passing' back to a 1 per cent, solution, tubes inoculated at the same 
intervals remained sterile. 

There seems to bean incompatibility between the first and last series. 
If we examine the others, however, we must conclude that the limit of 
disinfection lies between 1 and i^ per cent. 

Iodine 2vater was ])repared by shaking' up some iodine in distilled 
water, which assumed an amber tint. This solution destroyed the ba- 
cillus in fifteen minutes, as the following experiment shows: 

Six tubes were inoculated with bacilli after they had been exposed 
to the action of the iodine water for seven, ten, fifteen, twenty, twenty- 
six, and thirty-one minutes. On the following day the first tube became 
turbid; on the second the teuminute tube was turbid and found to be 
a i^ure culture of the bacilli sown. The other tubes remained sterile. 
One of the tubes, inoculated later, showed its capacity for sustaining 
growth by becoming prompt!}' turbid. 

Fennanganate of potash. —A series of experiments with this substance, 
conducted in the manner described above, showed that the bacillus is 
killed by fifteeu minutes' exposure to .02 j)er cent, solution (1 : 5000). 

In order to obtain this result a 5 per cent, solution was tried first. 
Tubco inocidated after an exposure of the virus for seven, ten, fifteen, 
twenty, twenty-five, and thirt^^-one minutes remained permanently clear. 
One of these tubes, subsequently inoculated with the unaffected virus, 
was turbid next day. Two and a half percent., 1 per cent., one-half 
per cent., one-fourth per cent., one-tenth per cent., and one-twentieth 
per cent, solutions were tried in the same way. The six tubes used for 
each solution remained sterile. Finally, a one-fiftieth per cent. (1:5000) 
was used. Tubes were inoculated after an exposure of the virus for 
two, four, six, ten, fifteen, twenty, twenty-five, and thirty minutes. On 
the following day the four first tubes were turbid ; the fifth and seventh 
remained sterile; the sixth and eighth contained a fine bacillus. The.se 
two tubes, as was found later, belonged to a lot which, through some 
carelessness, had not been properly sterilized, and tiie majority became 
turbid before use. 

Mercuric iodide was found to destroy the bacillus in solution of 
1:1000000 in ten minutes. 

Two grams of potassium iodide and 1 gram of mercuric iodide were 
dissolved in 100 cubic centimeters of distilted water, making a 1 per cent, 
solution of the disinfectant in a 2 per cent solution of potassium iodide. 

This solution, diluted with sterile distilled water so as to make .1 per 
cent., killed the bacillus of hog cholera taken from liquid cultures in 
less than five minutes ; .01 per cent. (1 : 10000), .002 per cent. (2 : 100000), 
.001 per cent. (1 : 100000), and .0005 per cent. (5: 1000000) destroyed the 
germ within two minutes. 

When the solution was diluted so as to make .0002 per cent. (2 : 1000000) 
and .0001 per cent. (1 : 1000000), it was found that with both solutions 
tubes inocidated with bacilli, after an exposure of two and five min- 
utes, were opalescent, the bacilli introduced having multiplied, while 
the remaining tubes (ten ti> thirty minutes) were sterile. These two 
solutions, therefore, were still powerful enough to kill the germ in ten 



90 

minutes. Tlie dilation Lad been carried so far as to make tliem prac- 
tically equivalent in disinfectiug i)ower. 

Sulphate of copper. — Tliis disinfectant, which seems to be more effect- 
ive than most other nutallic salts, was tried in solutions containing 2 
per cent., one-half per cent., one tenth per cent. Both the 2 per cent, 
and the one half per cent, solutions destroyed the germ within five 
minutes. Tubes inocuhited with bacilli after an exposure to the one- 
tenth per cent, solution lor five, ten, and fitteen minutes, became tur- 
bid ; tLose inoculated alter an exposure of twenty, twenty-five, and 
thirty minutes remained clear. 

The disinfectant power for short periods of time may be said to lie 
between one-half and one tenth per cent. Tn this, as in other tests, one 
or two droi)s of the culture were added to 5 cubic centimeters of the dis- 
infectant. A slight flocculent precipitate formed each time. 

Of hyrlrochloric acid a .2 per cent, solution of the acid, made by adding 
4.2 cubic centimeters of chemically pure acid (containing about 40 per 
cent. HGl) to l)a.8 cubic centimeters of water, destroyed the germ in 
less than five minutes. 

Chloride of zinc. — A 10 per cent, solution of this salt failed to destroy 
the vitality of the bacilli in ten minutes; 20 cubic centimeters of (Squibbs) 
chlorideofziui', containing .50 per cent, of the salt, were added to 80 cubic 
centimeters of sterile distilled water, to make a 10 ])er cent, solution. A 
drop from a culture five days old was mixed with G cubic centimeters of 
this solution, from which mixture tubes were inoculated at the end of 
five, ten, fifteen, twenty-five, and thirty minutes. The two first tubes 
became clouded. 

Sulpihvric acid. — A .05 per cent, solution (1 : 2000) w'as fatal to the ba- 
cilli of hog cholera in less than ten minutes. 

Without going into detail, it is sufficient to say that the results weie 
reached as indicated above. Tubes containing sterile beef broth were 
inoculated at the end of five, ten, fifteen, twenty, twenty-five, and tliii ty 
minutes with bacteria exposed to one-half per cent, and one fourth per 
cent. No development. Those inoculated with one-fortieth per cent. 
became clouded, each being a pure culture of the bacillus inoculated. 
When one twentieth per cent, was tried only the five-minute tube be- 
came clouded. The solution (by weight) was made from sulphuric aoid 
containing 96 per cent, of the acid (specific gravity 1.838). 

It must be remembered that the foregoing tests were made upon bac- 
teria in an active, vegetative state. It is probable that in the dried con- 
dition it would have taken solutions of the same strength somewhat 
longer time to destroy their vitality. To briefly summarize the results, 
placing the least-effective substance first, we obtain the following table : 

Chloride of zinc in a 10 per cent, solution destroyed the bacilli in 
liquid cultures in fifteen minutes. 

Carbolic acid, 1 to 1^ percent. (1:100), in five minutes. 

Iodine water, in fifteen minutes. 

Hydrochloric acid, one fifth per cent. (1:500), in less than five minutes. 
(Only a .2 per cent, solution of this acid tried.) 

Sulphate of copper, one-tenth per cent. (1:1000), in fifteen to twenty 
minutes. 

Sulphuric acid, one-twentieth per cent. (1:2000), in less than ten min. 
utes. 

rermanganate of potash, one-fiftieth per cent, (1:5000), in fifteen 
minutes. 



91 

Mercuric chloride, one seven liuiulrcd and fiftietli i>er cent. (1:75000), 
less than five minutes. 

Mercuric iodide in one ten-tbousaudtli per cent. (1:1000000), in ten 
minutes. 

The above table would without doubt be very materially altered if the 
test had been made with virus mixed with considerable organic matter. 
This is very well illustrated by the experiments on lime, crude carbolic 
acid, and additional experiments on sulphuric acid, given in full in the 
following pages. IMercuric chloride, for instance, often fails completely 
in albuminous liquids, although it is one of the best destrnctix'e agents 
of bacteria suspended in water. So permanganate of potash, which 
would have little or )io disinfectant power in liquids highly charged with 
organic matter, has a very high power in this direction iu the experi- 
ments detailed above. 

The only substances iu the above list, which, iu our estinuitiou, would 
be useful for purposes of disinfection, are mercuric chloride and car- 
bolic acid. Of the former, more will be said iu discussing the subject of 
prevention. Carbolic acid as it usually appears in the market is too ex- 
pensive tc^be used on a large scale. 

CRUDE CARBOLIC ACID. 

Laplace {Deutshe Med. Wochcnschrift, 1888, 121), found that the so- 
called crude carbolic acid, which will not dissolve in water, is capa- 
ble of solution when mixed with an equal volume of commercial sul 
phuric acid. A -L per cent, solution in water of this mixture was suflti- 
cient to kill anthrax spores within forty-eight hours, and a 2 per cent, 
solution destroyed them within seventy-two hours. Pure carbolic acid 
in a 2 jier cent, solution has no effect on anthrax spores. The crude 
material contains about 25 jier ceot. of carbolic acid. Experiments were 
made to test the germicide effect on hog cholera bacilli. The crude car- 
bolic acid used was a very dark, reddish, thick liquid, smelliug strongly 
of tar, and not translucent even in a layer one-half inch deep. When a 
drop of this liquid was added to water it broke up into a few globules, 
which settled to the bottom without undergoing solution. When an 
equal volume of commercial sulphuric acid was added and the mixture 
thoroughly shaken, a few drops added to water caused a faint turbidity, 
but none remained iu a globular condition. When more was added the 
water assumed a grayish, opalescent appearance, similar to water in 
which a small quantity of soap is dissolved. 

To test this mixture, a culture liquid was prepared like that used in 
testing the disinfecting power of slaked and unslaked lime. (See p. 
90.) Beef infusion (to which the white of an egg was added in the pro- 
l^ortion of one egg to COO cubic ceutiuieters of the infusion) was neutral- 
ized and sterilized without previous filtration at 110° C. iu Erlenmeyer 
tlasks, containing each about 150 cubic centimeters. This turbid liquid, 
with its large quantity of flocculeut material, was inoculated with hog 



92 

cholera bacilli and allowed to stand for a week. Each flask then re- 
ceived a certain quantity of the mixture and was thoroughly sliaken up. 
After certain intervals of time a jdatiuum loop of liquid was withdrawn 
from each flask, mixed with gelatine, and a roll culture made to indi- 
cate tbe number of surviving bacilli. To make sure of the vitality of 
the bacilli in the culture a control culture was made from one of the 
flasks before adding the disinfectant. 



Flasks with 150 cubic centimeters culture-liquid, to which was added of 
the mixture of carbolic and sulphuric acids — 



J cubic centiraeter=J per cent, (vol). 

IJ cubic centimeters=l per cent 

2i cubic centimeters=l § per cent 

3 cubic centimeter8=2 per cent 

Check tube 



Number of colonies in roll 
cultures at the end of— 




The table shows that a one-half per cent, solution by volume is suffi- 
cient to destroy the bacilli within one hour. What share the'sulphuric 
acid has in determining this result can not be inferred unless tried by 
itself under precisely the same conditions. Tbis is what has been done 
in the following experiment: 

Five Erlenineyer flasks, containing each about 150 cubic centimeters 
of a culture fluid prepared precisely like that in the preceding experi- 
ment, were inoculated with hog cholera bacilli and allowed to stand at 
a temperature of 70° to S(P F., for lour days. At the end of this period 
each drop of the culture medium, as ascertained by roll cultures, con- 
tained countless bacteria. Commercial sulphuric acid was added fiom 
a sterilized burette to the flasks in defiiiite in-oportions by volume and 
roll-cultures made at the end of one, two and a half, tweiitylbur hours, 
and four days by transferring a minute quantity of the agitated culture 
on a platinum loop. 

The accompanying table indicates the result obtained, the specific 
gravity of the acid being 1.84-- 



Volume of sul- 
phuric acid 
added to 150 
c. c. culture- 
liqiiid. 


Per cent. 

by 
weight. 


Check. 


Number of colonies in roll cultures .at the end of— 


Ouc hour. 


"ES' ^-:£?- 


Four days. 


c. c. 
.2 

.4 

.95 
1.7 
3 


.24 

.48 

1.14 

2. 04 

3.6 


Countless . . 
...do 


Countless. .. 
30 

None 

do 


Countless .. 

10 

3 

None 


100 

None 

.. do ... .. 
... do 


None. 
Do. 
Do. 
Do. ' 
Do. 




do 


...do 


...do 









93 

One half per cent, of sulplmric acid (by weiglit) is thus sufficient to 
sterilize a richly albuminous liquid in three to four hours. Kemeniber- 
ing that in the crude carbolic acid mixture the per cent, of sulphuric 
acid (by weight) contained in the one half per cent, solution (which was 
capable of sterilizing a simih^r liquid in one hour) was .oO, we must 
conclude that there can be no great difference between the crude car- 
bolic acid mixture and the sulphuric acid in regard to disinfecting 
power. We shall, however, recommend the former in disinfection, since 
it may lust longer in the soil in which sulphuric acid soon forms sulphates 
and thereby loses its germicide properties. According to experiments 
giveu ou page 90, .05 per cent, sulphuric acid was sufficient to destroy 
hog cholera bacilli in ten minutes when no organic matter was present. 
In the above experiment, in which the liquid contained much organic 
matter, about ten times as much was necessary. 

ORDINARY LIME AS A DISINFECTANT FOR HOG CHOLERA. 

Eecent experiments made with ordinary lime (CaO) by Liborius 
{ZeitscJinff f. Hygiene II, 1887, p. 15) have shown that water containing 
but .0074 per cent, of lime is capable of destroying typhoid bacilli in the 
course of a few hours. Cholera spirilla are destroyed by a solution con- 
taining .0246 per cent, of lime. These two diseases resemble hog chol- 
era in the mode of dissemination of the virus. In all, the stools are the 
chief vehicle of the bacteria. Disinfection, therefore, becomes a most 
important aid in the prevention of the disease. 

Lime has many advantages over other disinfectants. It is, first of all, 
not poisonous. It may be used almost anywhere with imi^unity where 
mercuric chloride or strong acids are inapplicable. The soil, when 
containing the germs of the disease, is not injured by being covered 
with a small quantity of powdered or slaked lime. The material is ex- 
ceedingly cheap and can always be obtained without difficulty. The 
experiments given in the following images show that lime is a very effi- 
cient disinfectant with reference to hog cholera virus, and therefore with 
reference to the bacteria of swine plague, which are far less resistant 
than the former. 

The method is, in the main, based upon that used by Liborius, with 
some modifications, which it is not necessary to point out here. 

(1) It was desirable to observe what percentage of lime in solution 
was necessary to destroy hog cholera bacteria not mixed with any ap- 
preciable quantity of organic matter. For this purpose water contain- 
ing different quantities of lime in solution received about two drops from 
a beef-infusion culture, each drop containing approximately 500,000 bac- 
bacteria. Attheeudof one-half hour aboutone-thirtiethcubiccentimeter 
of the fluid (usually 8 to 10 cubic centimeters) was removed with a flamed 
platinum spiral and transferred to liquefied gelatine in a test tube. The 
same was done at the end of three hours. This tube was then placed in 
ice water and twirled between the fingers while in a horizontal position. 



94 

The gelatine, as it coiigealecl, uiiifornil.v coated the luside of tbe test tube, 
wliicli was immediately trausfericd !o a box in connection with a refrig- 
erator, where it was kept at a temperature of 75° F.* The temperature of 
the laboratory during these experiments was frequently as high as 95° F., 
scarcely ever below S(P F., (July). Any bacteria not killed by the disin- 
fectant would show as minute yellowish-white points in the layer of gel- 
atine within forty-eight hours. The number of points corresponded to 
the number of living bacteria introduced into the gelatine. These cul- 
tures will be denominated roll cultures in the succeeding images. By this 
method it was found that lime-water diluted with three times the quan- 
tity of distilled water was sufficient to destroy hog cholora bacteria in 
one-half hour. A dilution containing six times the quantity of water 
destroyed the bacteria in three hours, while a dilution containing twelve 
times the quantity of water was not capable of destroying them in 
twenty-four hours. 

If we take .12 per cent, as the quantity of lime in lime-water, .03 per 
cent, of lime will destroy all bacteria in one-half hour, .019 per cent, in 
three hours. 



Lime-water diluted so as to contain of CaO. 



0.072 per cent . 
O.OG per cent .. 
0.04 per cent.. 
0.03 per cent. 



Number of colonies in 

roll cultures prepared 

at the end of — 



Liquid cultures 

inoculated at 

the end of 

twenty-four 

hours. 



Check tube Countless 




II. 



0.03 per cent | None. 

0.010 per cent 

0.0092 per cent 

Check tube 



Very many. 
....do 

Countless. 



None 

....do ■ 

Very many 



Sterile. 
Do. 
Turbid. 



* Contains hay bacilli. 

The quantity of the disinfectant used must be increased, with many 
disinfectants, with the quantity of organic matter present in the mate- 
rial to be disinfected. The preceding experiment gives us therefore 
only the minimum quantity that is necessary to destroy hog cholera 
bacilli when organic matter is practically absent. 

A second series of experiments was therefore made by mixing beef 
infusion cultures with varying proportions of lime-water, and observing 

*A (iescriptiou of this method is given by it^ author, .^, Esmarch, iu the '/^eitschrift 
fur Hijfjiene, i (1886), Tp. 293, 



95 

the quantity necessary to destroy all bacteria present. A preliminary ex- 
periment was made by adding- lime water in varying proportions to cult- 
ure tubes containing about 10 cubic centimeters each of beef infusion 
which had been inoculated the day before and were now opalescent. A 
tlocculent precipitate formed after the addition of the lime-water, which 
soon settled to the bottom, the quantity of this precipitate varying di- 
rectly with the amount of lime water added. The following table shows 
that in all the cultures macle by transferring a loop of tlie mixture of cult- 
ure liquid and lime-water in the proportions there given at the end of 
thirty minutes, four hours, and twenty-seven hours, no destruction or 
retardation of bacterial growth could bo detected. In the first tube con- 
taining beef infusion and lime-water in the ratio of 2 to 1 the precipitate 
left at first a perfectly clear supernatant liquid. This did not, however, 
mean complete disinfection, as the roll cultures proved. Moreover, at 
the end of three or four days this liquid became opalescent again, owing 
to the rapid unchecked multiplication of the contained bacteria. 

A quantity of lime amounting to .04 per cent, was not sufficient to 
destroy the vitality of beef infusion cultures. 

III. 



a 
o 

a) 


Lime 
water. 


Lime. 


Number of colonies in roll cultures prepared at 
the end of — 


One-half 
Lour. 


Four 
hours. 

■ 


Twenty-seven 
hours. 


Seven days. 


c. c. 
10 
10 
10 
10 
10* 


c.c. 
5 

1 
i 


Per cent. 
.01 
.02 
.01 
.0057 


Couutkss 
. . do 


Countless 
...do 


Countless 

. do . 


Countless. 
Do 


...do .... 
...do ... 
...do .... 


... do ... . 


...do 


■ 


...do .... 


....do 






r-. 









* Check. 

This experiment was therefore continued with relatively larger quan- 
tities of lime. Four portions of 40 cubic centimeters each of beef infu- 
sion in culture tlasks, in which hog cholera bacteria had multiplied for 
twenty-four hours, were mixed respectively with one-half, one, one and 
one-half, and two volumes of lime-water, and thoroughly shaken. It 
was found by testing with roll cultures at the end of thirty minutes, four, 
and twenty-seven hours that for every 40 cubic centimeters of culture 
liquid it required GO cubic centimeters of lime-water to destroy all bac- 
teria within twenty-seven hours, while a large number were destroyed 
within four hours. It required 80 cubic centimeters to completely- ster- 
ilize the culture fluid in four hours, although nearly all bacteria were 
destroyed within the first half hour. In the flask to which 40 cubic 
centimeters had been added there was a partial destruction of bacteria 
at the end of twenty-seven hours. At the end of six days the bacteria 



96 

were as numerous as in the flask coutainiug 20 cubic centimeters of 
lime-water, in which uo destruction of bacteria or retardation of growth 
could be observed. The percentage of lime in these cultures is given 
in the following table : 

IV. 



a 

o 

a 
a 

M 

c. c. 

40 
40 
40 
40 


Lime- 
water. 


Lime. 


Nui:ber of colonies in roll cultures prepared 
at the end of— 


One-half 
hour. 


Fourhours. 


Twenty- 
seven 
hours. 


Six days. 


c. c. 

20 
40 
CO 
80 


Per cent. 

.04 
.00 
.072 
.08 


Countless . 
....do 


Countless . 
....do 


Countless . 
Very many. 

None 

...do ... 


Countless. 
None. 


....do 

A few .... 


A few 







When the lime-water was added to the beef infusion a light flocculent 
})recipitate was formed immediately as in the preceding experiment, 
the quantit.y depending on the amount of lime-water added. This set- 
tled to the bottom in a very short time, leaving a perfectly clear, slightly 
yellowish layer of liquid above. In those flasks, however, iu which dis- 
infection was not accomplished, this layer of liquid remained turbid, or 
else became clear at first, with the partial destruction or precipitation 
of bacteria, and then became clouded again as the remaining bacteria 
multiplied in it. 

The quantity of organic matter which is present iu substances to be 
disinfected is ordinarily quite large. This is true of bowel discharges 
which contain the specific hog cholera bacteria, and which should there- 
fore be thoroughly disinfected. To prepare a solution containing a con- 
siderable amount of insoluble albuminous matter, the method of Liborius 
was adopted. Beef was chopped finely and allowed to soak over night 
in the refrigerator in twice its weight of water, as in the preparation 
of beef infusion. After the meat had been removed from the liquid 
in a press the latter was neutralized and the white of an egg was 
added in the ratio of one Q:g,g to every 600 cubic centimeters of liquid. 
The whole was boiled and the coagulated masses allowed to remaiu in 
the liquid. The amount of solid particles and lumps, when deposited 
on the bottom, formed a layer nearly as deep as that of the liquid above 
it. 

This mass of liquid and solid matter was placed in Erlenmeyer flasks, 
each receiving 150 cubic centimeters. The whole was sterilized for sev- 
eral hours at a steam pressure of 12 pounds and subsequently inoculated 
with hog cholera bacteria. At the end of three days, when each drop of 
the culture liquid contained nearly a million of bacteria, milk of lime, 
made by adding lime in the ratio of one gram to 9 cubic centimeters of 



97 

water, or, iu other words, milk of lime coutaiuiDg 10 per cent, of lime, 
was added iu various quantities as sbowu by the following table; 



No. 


Beef infusion. 


Milk 




Number of colonies in roll cultures made 
at the end of — 


of Lime. 
Lime. 


One-half 
hour. 


Tliiee 
hours. 


Twenty- 
four 
hours. 


Six days. 


1 
2 

4 
5 


c. c. 
150 
150 
150 
150 
150 

(§) 


c. c. Per cent. 
40 2.1 
20 1.2 


None 

...do 

...dot .... 
....dot .... 
Very many. 

Conntles.s. 


None* 

....do 


None ... 
..do 


None. 
Very many. 


10 
5 
2 


.62 
.32 
.13 


....do 

....do 

Very many. 


. . do . . . 

....do .. 
50 







'■About 12 funsi. 



t About 100 fuiisi. 



§ Check (beef infusion). 



In all the experiments the cultures coutaiuing tiie preci])itated mat- 
ter were shaken up before testing so that the quantity taken for the 
roll cultures (about ^j^ to J„ cubic centimeter on a spiral ot platinum) 
consisted of solid particles as well as liquid. 

Within thirty minutes after the addition of the milk of lime the pre- 
cipitate had settled so as to leave the supernatant liquid perfectly 
clear in flasks 1, 2, and 3; in flasks 4 and 5 it was still tuibid as be- 
fore the addition of the lime. It cleared up in Ko. 4 soon after, but re- 
mained permanently turbid iu No. o. In none of the other flasks did 
this layer become turbid even after seven days. In these the bacteria 
were permanently destroyed, as the table shows. That the lime trans- 
ferred to the roll cultures could have had no retarding effect on the 
growth of any bacilli present was proved by adding at least four times 
the quantity of lime to a gelatine tube which had been inoculated with 
a drop of culture fluid. Countless colonies appeared in the gelatine 
layer in due time. The check tubes were tested o dy at the beginning 
of every experiment to test the vitality of the cultures used. Since hog 
cholera bacteria will remain alive m the beef infusion employed for 
weeks and months, there was nothing to be gained in making loll cult- 
ures from these check tubes more than once. 

The table shows that 5 cubic centimeters of a 10 per cent, milk of 
lime was sutBeient to sterilize within one-half hour 150 cubic centime- 
ters beef infusion containing much suspended albuminous matter. This 
would be equivalent to about one half gram of ordinary unslaked lime, 
or about .0032 gram for every cubic centimeter of liquid, i. e., .32 per 
cent. We may assume, therefore, that for every twenty pounds of 
fecal matter or discharges from diseased pigs only one ounce of lime 
in the form of milk of lime is needed, provided the two are thoroughly 
15G12 II c — -7 



98 

mixed. The less complete this mixing- can be the more lime must be 
added to make the disinfection thorough. By compariug the amount 
of lime necessary when there is little or no albuminous or other organic 
matter present and when there is a large quantity of it, we are im- 
pressed with the importance of alwaj'S taking into consideration the 
circumstances under which disinfection is to take place. Thus the 
bacteria of hog cholera are destroyed in one-half hour when placed 
in water containing only .03 per cent, of lime. When there is i)resent 
beef infusion diluted to one third the original strength it requires .08 
per cent, of lime. When the suspended albuminous matter is consid- 
erable it requires .32 per cent. 

It may be more convenient to use unslaked lime either in small lumps 
or powdered shortly before application to the mass to be disinfected. 
That this may be done the following experiments are sufficient proof: 

Erlenmeyer flasks, containing each from 100 to 200 cubic centimeters 
of beef infusion in which there was a large amount of suspended mat- 
ter, as in the preceding experiment, were used for this purpose. After 
inoculating each with hog cholera bacteria they were allowed to stand 
for forty-eight hours. At the end of this time the flasks contained raanj^ 
millions of germs in each cubic centimeter. Unslaked lime was broken 
up into lumps as large as peas or beans, and thoroughly heated over a 
Buusen flame to destroy any adherent spores and drive away any moist- 
ure. After cooling, this was thrown into the culture-flasks in the pro- 
portion, by weight, of 2, 1, ^, and | per cent., respectively. The flasks 
became very slightly warmer. After thorough shaking the sus[>ended 
matter soon began to settle down, leaving a clear, supernatant liquid, 
which remained clear after ten days' observation. The liquid in the last 
flask (^ per cent, lime) cleared up most tardily. The attached table shows 
that even as little lime as .^ gram in 100 cubic centimeters was sufficient 
to x)ermanently destroy all bacteria in a liquid very ricli in albuminous 
substances. Even at the end of eight days the flasks containing the 
smallest amounts of lime were s'terile. * 

VI. 



Beef infusion. 


Percent, 
of CaO. 


Number of colonies developed in roll culture pre- 
pared with j'j cubic cenlimetor ot infusion at the 
end of— 




One hour. 


Four liours. 

None 

A fow 

Xono 

... do 


Twenty- 
four hours. 


Eight day.s. 


100 cubic centimeters plus 2 grams CaO . 
120 cubic centimeter.s pi us 1.2 grams CaO 
200 cubic centimeters plus 1 gram CaO. 
200 cubic centimeters plus .5 gram CaO. 


2 

1 

.5 
.25 


None 

....do 

Very r.! an J. . 
...do 


None 

. do 

, . do 

.. do 


Noue. 
Do. 



The table shows that in the flasks containing one-half and one-fourth 
per cent, of lime there were still a considerable number of living bacteria 



99 

at the end of the first hour, altlioui;li destroyed at the eud of four hours. 
The presence of bacteria in the fiask containing 1 per cent, of lime at 
the end of four hours, although none were detected at the end of the 
first hour, shows that all bacteria are not necessarily destroyed simul- 
taneously. 

A second experiment, conducted precisely as the preceding, confirmed 
the latter in every respect. The quantities were chosen somewhat dif- 
ferently, as the appended table shows, in order to find out the lowest 
percentage of lime that will destroy all bacteria within a given period 
of time. 

VII. 





Lime. 


Number of colonies in roll cultures made with jV 
cubic centimeter of the beef infusion at tliie 
eud of — 


Beef infusion. 


One hour. 


Three hours. 


Twenty- 
four 
hours. 


Five 
days. 


100 cubic centimeters plus 1 grain CaO 

200 cubic centimeters plus 1 gram CaO . . . 
200 cubic centimeters plus . 5 gram CaO . . - 
200 cubic centimeters plus . 3 gram CaO . . . 


Percent. 
1 

-J 
.15 


Very many . 

None 

Very many . 
Countless. .. 
....do 


None 

....do 

50 

Very many.. 


None . . . 

...do.... 

...do.... 

50 


None. 
Do. 
Do. 
Do. 











The lime was powdered, and heated in a platinum evaporator to de- 
stroy all adlierent spores. There was scarcely any perceptible rise of 
temperature when the lime was added to the liquid. The first flask con- 
tained a culture eight days old, the remainder contained cultures four 
days old. From the table it will be seen that one-half per cent, of un- 
slaked lime is sufficient to sterilize a very turbid albuminous liquid in 
four hours, one fourth per cent, in twenty-four hours. Fifteen-huu- 
dredths percent, was almost enough to destroy all the ge^ms in one daj" 
while at the end of five days all were dead. 



DISINFECTION OF THE SOIL WITH LIME. 

The same fine loam used in the experiments to determine the vitality 
of hog cholera bacteria in the soil was nsed here. The method pur- 
sued was briefly as follows : 

Into small beakers, plugged with cotton wool and sterilized at 150° 
C. for several hours, about 50 grams of slightly moist soil was intro- 
duced, and the whole sterilized under steam pressure at 110° O. About 
10 cubic centimeters of a beef-infusion culture of hog cholera bacteria 
was then stirred up with it. After a certain length of time milk of 
lime was added and thoroughly mixed with the soil. The destruction 
of the bacteria was noted at certain intervals of time by taking small 
bits of the soil on a platinum loop and making roll cultures therefrom. 



100 

The table appended gives the results of a series of experiments carried 
out according to tliis plan : 





Quantity 
of lime 
in soil. 


Check 
culture 


Number of colonies in roll cultures prepared from a small 
bit of soil after— 


Number aud date of 
experiments. 


One-half 
to one 
hour. 


Three 
to four 
bours. 


One 
day. 


Two 

days. 


Three 
days. 


Five 
days. 


Six 
days. 


Seven 
days. 


1888. 
T.— Jan. 18 


Per cent. 
1 
2 

h 
i 
i 
i 

i 

i 
1 

2. 

4 

1 


'oo 

GO 

00 
00 

00 

(') 
(') 

00 
00 
00 
00 


100 
■10 

{') 
(-) 

00 




30 



2.30 




12 

n 


















II.— Jan. 20 










III. -Jan. 23 


3-4 
1000 
20 
8 










GO 




10 








I v.- Jan. 24 









v.— .Jan. 31 






00 


C) 


VI.— Jan. 31 

VII.— Feb. 10 










00 




Vni.-Feb.lO 

IX. -Feb. 23=.... 




(*) 







X.— Feb. 23 5 








XL— June 7'- ... 
XII.— June?' 




















' Countless colonies. 

2 Less than oc, but still too numerous too be esti- 
mated. 
^ Fungi present. 
■* A few fungi present. 



= Babbit died of hog chokr.i aftir inoculation 
with soil on nineteenth day. 

^ A microccus multiplies in the soil. 

' Kabbit inoculated with soil on clcveuth day 
remains alive. 



Tlie following may serve to explain more fully the tabulated experi- 
ments and results obtained: 

I. Fifty grams sterile moist soil, infected with 10 cubic centimeters 
of a beef-infusion culture January 5. January IS: 5 cubic centimeters 
of a 10 per cent, milk of lime (9 cubic centimeters water and 1 gram 
ordinary unslaked lime) was stirred up with it. This is equivalent to 
1 per cent, of lime. A roll culture from the infected soil was made in 
all exi)eriments before the lime was added, to make sure of the pres 
ence of living germs. • Eoll cultures, to which three loops of milk of lime 
were added, showed no diminution in the growth of colonies, ])roving 
that the small amount of lime (fraction of a loop) added with the soil had 
no retarding effect. In this experiment 1 per cent, lime was suflicieut 
to remove from the soil countless bacteria (as shown by check-roll) in 
three to four hours. 

II. January 20 : To another beaker of soil, prepared and infected with 
the preceding, 2 percent, milk of lime was added and stirred up. The 
result identical with Experiment I. 

III. January 23: 2i cubic centimeters of 10 per cent, milk of lime 
added (= .J percent.). The check-tube contains so many colonies as to 
have an opalescent appearance. Disinfection is nearly completed after 
one hour. A few colonies develop in the one day and three day tube. 

IV. January 21: 1| cubic centimeters of 10 per cent, milk of lime 
(= 1 per cent.); no disinfection is brought about. During the first 
twenty-four hours there is a decided diminution in the number of colo- 
nies, but a decided increase thereafter. 

V. VI. January 31 : The sterile soil in two beakers was infected yes- 
terday with a beef infusion peptone culture three days old, 10 cubic 
centimeters being added to each beaker. Today enough milk of lime 



101 

(5 per cent.) is added to two beakers to make one-lialf per cent, aud 
one-quarter per cent., respectively. The check tubes show subsequently 
countless colonies. The table shows a slight diminution in the number 
of colonies for the first twenty-four hours, then an increase. JS'o disin- 
fection. For the one-half per cent, beaker there is apparently a complete 
destruction during- the first two days, but subsequently the few remain- 
ing multiplied again. No disinfection here. This result seems to disa- 
gree with the third experiment. The discrepancy was, however, caused 
by the fact that the milk of lime was not thoroughly shaken up when 
used. 

YU, VIII. In these experiments the lime was thoroughly stirred up 
before use, and in both beakers disinfection has taken place. The 
germs in the soil before adding the lime were not so numerous, because 
the soil had been infected from a liquid culture only fifteen minutes 
previous and no multiplication could have taken place. 

IX, X. The conditions of the experiment are the same as before. 
The soil is infected with a liquid culture two days old. Seven days 
later check-tubes are prepared from each beaker of soil. One receives 
one-half per cent, lime, the other three-quarters per cent. {I. e., 5 cubic 
centimeters and 7.5 cubic centimeters of a 5 per cent, milk of lime to 50 
grams soil). The table shows that the beakers were invaded by a mi- 
crococcus after the first day, which multiplied enormously in the soil, 
so that hog cholera colonies could not be detected. After nineteen days 
two rabbits, inoculated with a little infusion made from the soil, suc- 
cumbed to hog cholera. 

March 13: Eabbit inoculated subcutaneously with sterile beef infusion, 
in which a little of the one-half per cent, lime soil had been stirred up. 
Kabbit dead March 19. Spleen enlarged, congested; kidneys, lungs, 
and duodenum with hemorrhagic foci. Beginning necrosis in liver. 

A second rabbit inoculated from the three-quarters per cent. lime soil 
in the same way and at the same time. Eabbit dead March 21. Lesions 
the same, in addition to a hemorrhagic condition of the lower portion of 
large intestine. In both hog cholera bacteria present. 

XI, XII. Experiments carried out as the preceding ones. The bac- 
teria were permanently destroyed, as shown by the roll cultures made 
up to the seventh day, and unsuccessful inoculation of rabbits later on 
the eleventh day. 

From these experiments we may conclude that three-quarters to one 
per cent, of lime will destroy hog cholera bacilli in the soil. It is highly 
probable that a smaller per cent, of lime (one quarter to one-half per 
cent.) will be amply sufficient when simply scattered in a thin layer 
over the surface where the great majority of tlie disease germs will 
remain until destroyed by natural agencies. 

IS THERE ANY RESISTANT SPORE STATE IN THE LIFE HISTORY OF 
THE BACILLUS OF HOG CHOLERA? 

This question can now be answered with the help of the foregoing 
experiments. 

Stained in dilute aqueous solutions of aniline colors the bacilli from 
the tissues of animals which have succumbed to the disease stain in 
such a way as to leave the impression that each bacillus contains an 
endospore. A narrow band of stained substance bounds an oval pale 



102 

body, which is but slightly tiuged. It appears that a rather resistant 
envelope prevents the coloring matter from passing readily into the in- 
terior of the bacilli. 

If a drop from a recent liquid culture be suspended from the lower 
surface of a cover-glass and examined in a glass cell witli a homogene- 
ous immersion objective and. small diaphragm, the following appear- 
ances are worthy of record : The bacteria in the center of the drop of 
culture fluid are in very active motion. If the periphery of the drop be 
examined there will be found a dense layer of bacteria caught there by 
the slow desiccation and consequent contraction of the drop. These, 
some of which are still moving slowly, appear slightly larger than the 
forms in the center of the drop. As the drying proceeds and the film 
of water becomes thin, the bacteria appear to be made up of a distinct 
dark border surrounding an almost transparent body. In most forms 
there is a slightly thicker border at the ends than at the sides of the 
short, rod-like bodies. When stained slightly this border takes the 
stain well, while the body of the rod remains pale. The fact that the 
structural and color pictures correspond is strong evidence that the 
microbe possesses a rather dense membrane, which in optical section is 
seen as a narrow dark border. 

Involution forms may occasionally simulate endogenous spore forma- 
tion. When hog cholera bacilli are placed upon the surface of gelatine 
with a drop or two of blood, a few days are sufficient for the formation 
of a large number of filaments from two to many times the length of 
the bacilli as they are found in the tissues of animals. The ends are 
rounded or irregularly pointed ; the width of the bacilli varies ; in gen- 
eral, they have the physiognomy of abnormal forms. In each bacillus 
there may be from one to four oval, square, or oblong, clear spaces. 
When stained they remain without color, thus simulating spores. When 
carefull}' examined in a fresh condition, there isnorefrangibility — they 
are mere holes or spaces left by the irregular breaking up and retrac- 
tion of the protoplasm. 

Microscopical characters, however, are now aiid then misleading, un- 
less we interpret them by physiological experiments. Judging from 
what have hitherto been considered properties of bacterial spores, the 
microbe of hog cholera can not lay any claim to the production of true 
endogenous spores. Their absence is determined by results of experi- 
ments recorded in the preceding pages : 

(1) The thermal death-point of the bacilli at 58° 0. An exposure to 
this temperature for fifteen to twenty minutes destroys not only the vi- 
tality of cultures of all ages, but also the germ in the tissues of the in- 
fected animal. A momentary exposure to boiling water is equally effi- 
cacious. 

(2) The bacteria are destroyed by disinfectants in solutions which are 

incapable of destroying spores. 



103 

(3) They are killed by simple dryiug- far more quickly than are spores; 
at the same time their resistance to drying is much greater than might 
be expected under the circumstances. In the experiments recorded 
some dried bacteria in spleen pulp were killed in less than a month ; 
otheis resisted lorty-nine d,\ys. For cultures we may put the limit, ac- 
cording to experimental data, between one and four months. It is this 
continued vitality in the dried state that suggests the existence of a 
membrane which is more resistant than that i)Ossessed by the great 
majority of bacteria in their vegetative state. 

(4) Subjected to various conditions of moisture and dryness, of freez- 
ing and thawing in the snperticial layers of the soil, they are destroyed 
after an exposure of between two and four months. 

The facts brought out by the study of the bacillus lead to the con- 
clusion that a distinct spore state, so called, does not appear either 
within the animal body or in nature. 



WAYS IiN WHICH SWIiNE BECOME LNFECTED. 

BY WAY OF THE DIGESTIVE TRACT. 

(a) Feeding diseased viscera. — In at least 90 per cent, of swine, hog 
cholera may be induced by feeding to them the visceraof animals which 
have died of the disease. The lesions produced are exceedingly severe. 
The mucous membrane of the large, intestine is extensively ulcerated 
or comiiletely necrosed. In animals which have contracted the disease 
in the ordinary way in infected pens the ulceration of the large intes- 
tine, at times very severe, usually stops abruptly at theileo ca'cal valve. 
When this is slit up, the mucosa belonging to the small intestine up to 
the free border of the valve is in the great majority of cases normal, 
while the mucosa of that surface of the valve facing the ca-cum may be 
extensively ulcerated. In many animals fed with infectious matter the 
ulceration involves the entire ileum. This is well illustrated by the 
following cases : 

January 8, 1886. — Pig No. 1G5 was fed with the viscera of two i)igs 
which had died of hog cholera. It was found dead January 20, after 
manifesting no marked symptoms of disease except a tendency to lio, 
quietly in its pen. On examination the subcutaneous fat was found 
diffusely reddened. There was a slight peritonitis, indicated by a con- 
siderable quantity of straw-colored effusion and some fibrinous stringy 
deposits. There were also a few local excrescences on the small intes- 
tine, due to the irritation ot echinorhynclii, ISplcen somewhat enlarged ; 
on its surface a few bright red punctiform elevations. Eight heart dis- 
tended with a clot. Local hepatizations in lungs, probably caused by 
lung worms, which were very numerous. Stomach but slightly reddened. 
A numberof ulcers in the duodenum, the mucosa of which was reddened. 
The mucosa of the ileum for li feet from valve was completely ne- 
crosed, the walls thickened, and the serosa of this portion dotted with 
ecchymoscs. On the upper portion of the ileum there were scattered 
ulcerations on a deei)ly congested membrane for G or 7 feet. The entire 
length of the large intestine was covered with dirty, yellowish ulcera- 
tions varying in diameter from a pin's head to nearly an inch. The 
mucosa itself was very deeply congested in the caecum and colon, and 
the walls much thickened. Ascarides and eclmiorliijnchi num«»rous in 
small intestines. The liver attached to diaphragm in several places by 
a whitish exudate. 

A tube of meat infusion with peptone inoculated from the spleen of 
this animal was found to be a pure culture of the motile bacillus of hog 
cholera. Line cultures on gelatine plates confirmed the microscopic 
examination. A tube of nutritive gelatine inoculated from the spleen 
at the same time contained in each needle-track, several days later, 
from ten to fifteen colonies of the same organism. Two cover-glass pre- 
parations revealed no bacteria. This fact, combined tVith the small 
number of colonies in the tube culture, gave evidence of the small num- 

105 



106 

ber of germs in the spleen tissne. Inocnlations on mice and guinea- 
pigs gave substantially the same results as those obtained hitherto. 

No. 159 was fed with viscera of No. 1G5 on Januar^^ 28. Febru- 
ary 5, its eyes were sore and nearly closed ; it was quite weak. It died 
the following day, only eight days after infection. The skin ou ab- 
domen was reddened in patches; the subcutaneous tissue diifusely. 
The superticial inguinals, as well as the. glands in the abdomen, were 
deei)ly congested, the cortex more especially. Tliose of the thorax 
were nearly pale. The spleen was dotted with a few i)anctiform t)lood- 
red elevations. Beneath the epicardium and endocardium of both auri- 
cles and the endocardium of the left ventricle were extensive patches 
of extravasated blood. Kidneys enlarged and congested throughout. 
The lesions of the ileum, caecum, and colon in this animal were quite 
as extensive as those of the case just described ; there were no ulcers 
in the rectum, however. Those of the colon had black centers, point- 
ing to a recent origin from blood extravasations on the surface of the 
mucous membrane. 

In the spleen of this case the characteristic bacteria of hog cholera 
were exceedingly numerous, as determined by cover-glass preparations. 
Two liquid cultures proved pure when tested on gelatine plates. In the 
needle tracks of a tube culture in gelatine innumerable colonies ap- 
peared in afew^ days. Inoculations into animals from subsequent cult- 
ures proved equally positive. 

Pig No. 15C was fed with the viscera of No. 159 February 18, and 
after manifesting the usual symptoms of hog cholera, died February 
25, seven days after feeding. Among the marked lesions produced by 
the disease was a complete necrosis of the upper two thirds of the colon, 
with scattered ulcers along the lower third. Eight feet of the lower 
])ortion of the small intestine, beginning at the valve, was necrosed. 
In the spleen there were numerous small grayish spots, probably cen- 
ters of necrosis, as they showed no longer cell structure when crushed 
on a slide and stained. The fundus of the stomach was also deeply 
congested. 

The spleen, to which organ the microscopic examination was limited, 
contained the characteristic bjicteria, as shown b}' cover-glass prepara- 
tions. Three liquid cultures made from the same organ were found to be 
pure cultures of the same microbe when tested by line cultures. A tube 
culture in gelatine developed in each needle track numerous nonlique- 
fying colonies. 

In these animals the mode of introduction of the virus determined the 
seat of the severest lesions. It is probable that the food passes quite 
rapidly through the small intestine; that in the stomach the action of 
the bacteria is more or less limited, because they have not sufficient 
time to'multi[)ly, and probably because hindered by the acid condition 
of the organ, though they will multiply with considerable vigor in 
slightly acid solutions. The prolonged stay of the food in the large in- 
testine permits multiplication, and thereby causes the first and severest 
lesions to appear here. When these have become very extensive, so as 
to paralyze the action of the large intestine, the ileum becomes involved 
in a similar manner, possibly by a partial stoppage of the infectious 
matter in this portion of the intestine. 

It may therefore be said, in general, that the feeding of hog cholera 
viscera produces lesions like those found in natural infection, only more 



107 

severe and more extensive. The duration of tbe malady is also mucb 
shortened. The notes £;iven above are quoted from one of the reports 
of the Bureau. Since they were written numerous other pigs have been 
fed in this way in the course of vaccination and other experiments with 
precisely the same result. We must therefore emphatically deny the 
truth of statements made now and then in agricultural journals that hog 
cholera can not be communicated to healthy swine feeding upon the vis- 
cera of those dead from this disease. Such statements are pernicious 
in tendency, and aggravate the evil which this malady carries with it. * 
(b) Feeding imre cultures of hog cholera bacilli. — The successful re- 
production of this disease by feeding inue cultures of hog cholera bac- 
teria proves not only that the bacteria fed are the true cause of the 
disease, but also that infection may and does take place in this way. 
We again quote from the report for 1880 some experiments which 
demonstrate that swine may take the disease and die by simply swal- 
lowing somewhat more than half a pint of beef broth in which hog cholera 
bacteria were growing. 

December 13, 1886. — Three pigs were fed with 300 cubic centimeters 
each (three fifths of a pint) of a beef-infusion culture of liog cholera ba- 
cilli kept in the thermostat, at 95° F., for three days. The culture was 
contained in two flasks. When examined both Avere found pure. The 
l)igs were prepared for the feeding as follows: No. :U8 received no food 
for over twenty-four hours. A 2 per cent, solution of sodium carbonate 
in beef infusion was then given to increase the alkalinity of the stomach. 
Of this about 1 liter was consumed. It was then fed witli 300 cubic cen- 
tiuieters of culture liquid mixed with beef broth to make 1 liter. No. 
350 was starved in the same way, but received no alkali before consum- 
ing the culture. No. 312 was not deprived of food before eating the cult- 
ure. 

The result confirmed our anticipations. No. 348 showed signs of 
disease in two days. On the third it was unable to rise, and died on 
the same day. The post-mortem examination showed a considerable 
congestion of the mucous membrane of the duodenum and jejunum, as 
well as of the large intestine. The fundus of stomach affected in the 
same way. The liver was gorged with blood, as well as the portal 
system. There were no marked lesions of the other viscera. That hog 
cholera bacilli had also entered the blood was shown by two pure cult- 
ures in beef infusion obtained from the spleen. A gelatine culture 
from the liver contained about six or seven colonies. 

No. 350 was a more typical case, and demonstrated the severe local 
effects of the bacillus much better, since the animal lived longer. It 
ate fairly well until the fourth day, when its appetite gave way and 
diarrhea set in. From this time it grew weak and thin, being scarcely 
able to walk. It died on the tenth day after feeding. The lesions of 
the alimentary tract were exceedingly grave. Beginning with the 
stomach, the mucous membrane was dotted with closely-set elevated 
masses as large as split peas, and larger patches of a whitish viscid sub- 
stance, made up entirely of cellular elements (diphtheritic ?). When 
removed, a raw, depressed surface was exposed. The membrane itself 

* It may bo possible that those who make this claim vrerc coufiouted with swine 
plaj^uo. This disease, although I'escmbliiig hog cholera yery closely in many features, 
we have not been able to reproduce by feeding. 



108 

was pale. Besides a general injection of the ileum, Peyei's patches were 
more deeply congested, and the uppermost covered with a thin, yellow- 
ish film, not removable, and most likely dead epithelium. In the cae- 
cum and colon the mucosa was superficially necrosed, and converted 
into a continuous layer of a dirty whitish mass about 1"'°' thick. The 
walls of the intestine were greatly thickened and veiy friable. 

Microscoi^ic sections showed an extensive cellular infiltration of the 
submucous connective tissue which had separated the masses of fat 
cells, concealed the connective tissue fibers, and caused a great thick- 
ening of the entire layer. The mucosa itself was greatly altered. The 
surface was necrosed and converted into an amorphous mass. In some 
l)]aces the necrosis involved the entire depth of the crypts of Lieber- 
kiihu, a series of t^trite indicating their former existence. Those whose 
epitlielium still remained were plugged with a cylindrical nn\ss, inclos- 
ing broken-down nuclei. The bacteria had exerted their poisonous 
effects from the surface of the mucosa towards the dei)ths, destroying 
the surface epithelium and glandular structures and involving second- 
arily the submucous layer. Near the rectum this continuous mass of 
dead tissue was replaced by isolated ulcers embedded in an intensely 
reddened mucosa. The ileo-C5iecal valve was much swollen, but the 
necrosis did not extend into the ileum, although there were a few ulcers 
near the valve, and the epithelium had a pale, lusterless aspect, as if 
dead. The liver was filled with blood, which readily clotted as it flowed 
from the cut surface. Spleen congested and but slightly' enlarged. 
Lungs hypostatic. The lypmphatic glands in general not much aflected. 
Two liquid cultures from the blood were turbid next day, and contained 
hog cholera bacilli only. In a gelatine tube culture from the liver about 
a dozen colonies developed in each needle-track. 

No. 342, which was fed with the same quantity of culture licpiid, but 
was not deprived of food previously, was somewhat ill on the folio wing day. 
It recovered, however, and continued apparently well for several weeks. 
It began thereupon to grow thin and weak. On January 20 it was no 
longer able to rise, and was therefore killed for examination, in order to 
conclude the experiment. On opening the abdominal cavity it was at 
once perceived that the animal had been suffering from a very intense 
disease of the large intestine, ai)ortion of which was firmly attached to 
the bladder. When dissected out and slit open, the mucous membrane 
of the CiBcuin and colon was found replaced by a brownish friable layer 
of necrosed tissue. The wall of the intesMue was infiltrated to such an 
extent that it was nearly one-fourth inch thick, and so degenerated that 
the forceps easily' tore through it. The thickness of the walls pre- 
vented the intestine from collapsing- after it was opened. Its oidy con- 
tents was a brownish liquid mass. The glands of the nieso colon were 
very large, some like horse-chestnuts. On section the entire tissue was 
very pale, almost white. The spleen was somewhat enlarged ; the Mal- 
pighian corpuscles unusually large and prominent on section. Lungs 
and heart normal ; kidneys deeply reddrned throughout. 

This case is very interesting in completing the information gaiaedby 
this feeding experiment. No. 348, which had been fed with sodium car- 
bonate, besides being deprived of food, died three days after the ingest- 
ion of the culture. No. 350, which was simply starved, died ten days 
thereafter, while No. 342, which ate the culture without being previ- 
ously starved, was dying on the thirty-fourth day. 

These results show that infection may occur by way of the digestive 
system, provided the destructive action of gastric digestion be pre- 



109 

veuiC'd, lis was done by .stiirviiij;" and b^' the use of an alkaline car- 
bonate. 

They also indicate how purely local this destructive action maybe. 
Gelatine cultures from these animals showed that the internal organs 
contained but very few bacteria. So few were they in fact that the 
microscope alone could not have demonstrated their presence in the 
spleen. 

In addition to the cases given, equally positive results were obtained 
at four different times by the feeding- of pure cultures. Some of these 
results have been mentioned in otherplaccs (see page 207 of the Keportof 
Bureau of Animal Industrj' for 1885). It was also found that small 
quantities up to 100 cubic centimeters (^ pint) may be fed to moi^t pigs 
without obtaining any fatal results. Sometimes the fed animal becomes 
very sick, but recovers; sometimes no disturbance whatever is pro- 
duced. 

These experiments pro\e conclusively the causal relation between 
the bacilli of hog cholera and the disease so called. They show that 
pigs fed with nothing but sterile beef infusion, to whicli the minutest 
speok of growth from a hog cholera culture was added and in which the 
bacilli thus introduced were allowed to multiply ibr one or more days, 
were destroyed by a disease identical with hog cholera, but far more 
rapid in its course and more severe in its manifestations. 

SUBCUTANEOUS INOCULATION. 

Subcutaneous inoculation with hog cholera bacilli fiom cultures is 
successful in only a small percentage of cases, except when these germs 
are unusually virulerit. In the report for 1885 several cases of success 
fid inoculation are given, among which the following deserve to be 
briefly quoted: 

NovcDihcr 27, 1885. — Two pigs (Nos. 112, 114) were inoculated sub- 
cutaneously into the thigh with ,'3 cubic centimeters each of a jnire liquid 
culture. No. 114 died nine days after inoculation. The superficial ingui- 
nal glands were swollen, with hemorrhagic points in medulla. Spleen en- 
larged, dark. Extravasations on auricular appendages of heart. Lungs 
cedematous; bronchial glands enlarged, dark red throughout (hemor- 
rhagic). Glands of abdomen in general hemorrhagic, except those of 
mesentery ; petecchite under serosa of c;ecum. Kidneys with glomeruli 
appearing as blood-red points, the entire organ congested. Mucosa of 
fundus of stomach, lowest portion of ileum, and of the ca'cum and colon 
deeply reddened with slight extravasation. Cover-glass preparations as 
well as cultivations in gelatine and beef infusion revealed hog cholera 
bacilli, and these only. 

No. 112 died on the 15th day. Diairhea appeared two days before 
death. The lesions in this animal resembled those of No. J 14, with the 
ibllowing differences: Spleen very large, dark, friable. Kidneys less 
congested. Lungs with minute hemorrhages throughout the paren- 
chyma. Ecchymoses beneath the endocardium of left ventricle. Lym- 
phatics and digestive tract even more congested and hemorrhagic than 
in No. 114. 



no 

The success of tbese inoculations among numcrou , failures in subse- 
queut trials must be ascribed to the exceptionally virulent disease of 
that year, for noi cases have been observed since which died so sud- 
denly and i^reseuted such severe hemorrhagic lesions of the various 
vital organs. 

The following experiments, made with blood taken from the heart of 
swine affected with hog cholera and killed for the purpose, are taken 
from the report for 188G : 

September 10. — A pig dying with the disease was killed, the heart care- 
fully exposed, and the blood drawn with a disinfected hypodermic 
syringe. ISTos. 329 and 333 received subcutaneously 5 cubic centimeters 
each, one-half in each thigh. ]^o. 329 in a few days lost its appetite, be- 
came weak and stupid. Found dead October /i. Slight local swelling at 
the points of inoculation ; superficial iuguinals greatly enlarged; hypo- 
static congestion of lungs ; complete necrosis of mucous membrane in 
cjecum; large scattered ulcers in colon, showing as whitish patches on 
serous surface and encircled by a crown of enlarged blood vessels ; bac- 
teria in spleen. 

No. 333. Slightly ill for a time; fully recovered ; died December 2, 
with iro other lesions than engorgement of liver; no signsof former ul- 
ceration. 

A second experiment was made in the same way. 

October 13. — Nos. 324 and 325 inoculated as in the preceding experi- 
ment, 10 cubic centimeters of blood being used for each animal. No. 324 
was found dead November 1, after being off feed for a time ; deeply red- 
dened skin over caudal half of abdomen; sui)crlicial lymphatics ex- 
tremely hirge and serously infiltrated; on section, hemorrhagic points; 
at ])oint of inoculation the connective tissue is infiltrated ; 50 to 75 cubic 
centimeters clear amber serum in abdominal cavity ; i)ai)ill;e of kidneys 
deei)ly reddened ; slight congestion, but no ulceration in large intestine; 
lymphatics in general moderately tumefied and congested. 

No. 325 found dead October 29; reddening of skin as in 324; ex- 
travasation in connective tissue; spleen greatly enlarged, purplish; 
lymphatics of thorax and abdomen purplish — enlarged; petecchije on 
section of kidney and pelvis, also over entire surface of epicardium ; 
lung tissue mottled both on surface and on section with purple spots, 
due to blood extravasation into alveoli, so that it scarcely tloats ; mucous 
and serous surface of small intestine dotted with jietecchiie ; small hem- 
orrhages on the surface of the mucous membrane and into the submu- 
cous tissue of the caecum and upper colon; ulceration beginning. 

On first thought we might be inclined to attribute these successful 
lesults to a greater virulence of the germs in the injected blood. This 
>iew needs further confirmation, however. The injected blood coagu- 
lating in the connective tissue contains in it the bacteria, which are not 
only protected from the aggression of cellular elements, but have actu- 
ally a store of nourishment upon which they may live and nudtii)ly. 
No such advantages are presented to bacteria suspended in liquids 
which are readily absorbed, leaving them to the mercy of the tissues 
surrounding them. The local reaction in the above animals was very 
insignificant compared with that produced by liquid cultures. In order 



Ill 

to come to any conclusion it would be desirable to add a few bacteria 
from cultures to fresh blood, and observe tlic relative virulence by sub- 
cutaneous inoculation. 

Elsewhere in this volume will he found a small number of successful 
inoculations with pure liquid cultures among a large number of unsuc- 
cessful ones. The inoculations were made for the purpose of determin- 
ing whether they would confer immunity. In reading over these ex- 
periments it will also be seen that such injectious produce swellings 
varying from the size of a pea to a hen's egg. The tumor is developed 
in the subcutisaud consists of a yellowish white, tough tissue, breaking 
down in the center into a grumous mass alter a period of one or more 
months. 

In view of these facts we can not consider wounds or bites inflicted 
on the surface of the body a means of infection, excepting, perhaps, in 
epizootics of extieme virulence. Nor can we ascribe much influence to 
the stings of insects in inoculating the virus from one animal to another, 
as this would correspond to subcutaneous inoculations on a minute 
scale. Flies may, however, infect food in various ways, to be dwelt 
upon in subsequent pages. 

INTRA- VENOUS INOCULATION. 

The injection of hog-cholera virus (from the spleen of a pig examined 
near the city of Baltimore, Md.) into the circulation was tried but once, 
and this trial was successful in producing a hemorrhagic septicjemia 
such as we frequently encounter in outbreaks of the disease, and which 
proved fatal in less than three days. 

N'ovemher 12, 1888. — Pig No. 90, black and white, about five months old. 
The right crural vein was exposed by raising a triangular flap of skin 
over it after thoroughly disinfecting the latter with a one-fifth per cent, 
solution of mercuric chloride. Five cubic centimeters of a beef infusion 
peptone culture inoculated from an agar culture about a week old was 
injected into the exposed vein with a hypodermic syringe thoroughly dis- 
infected with 5 per cent, carbolic acid. The li(iuid culture was two days 
old when used. Two hours after the inoculation the temperature had 
risen from 103y F. to 107°. November 13 there was no swelling, but a 
slight serous oozing at the place of inoculation. The appetite was good. 
November 14, at 3 p. m., the temperature was lOTf. The animal was 
disinclined to move, although it came to eat in the morning and even- 
ing. November 15 it lay on its side quietly, with occasional kicking. 
Found dead at 4 p. m. Autopsy held immediately. 

General blush on skin of ventral aspect, snout, and lips. No swell- 
ing at the point of inoculation; slight blood extravasation. Spleen en- 
ormously enlarged, 14 inches long, 2 to 3 inches wide, and one-half 
to 1 inch thick, gorged with dark blood, and friable. Superficial in- 
guinals enlarged, (edematous; on section diffuse pale red spots; cortex 
congested. Bronchial and renal glands enlarged, partly hemorrhagic, 
gastric glands hemorrhagic throughout substance. The blood is thick, 
dark colored, coagulation slight, even after several hours' exposure to 
the air. Several petecchia^. on epicardium of right auricle. Kight side 
of heart distended with blood: in it a small Avhite clot. Left side 



112 

coutrauted, empty. Liiugs normal, cxceptiD<? oue-tliiid of left ventral 
lobe, which is eolhipscd. Kidneys cnhirged, deeply' congestrd Ihrongh- 
out. The surface is thickly dotted with minute deep red j)oints. The 
papillai. so deeply leddened that any extravasations would be unrecog- 
nizable. A few petecchiai in pelvis. Bladder contains about 30 grams 
of urine tinged with blood. The whole mucosa of stomach is deeply 
congested. In fundus it is hemorrhagic with numerous patches of nec- 
rosed epithelium one-fourth to one-half inch across. 

The upper 8 inches of duodenum in the same condition as the fundus 
of stomach. Numerous red points scattered over mucosa of entire small 
intestine. In lower ileum a few hemorrhagic points. The mucosa of 
ciccum and upper colon very slightly congested, but the remaining two- 
thirds intensely so. Hemorrhage here and there sufticient to stain the 
feces with blood which were otherwise normal. The mesenteric and 
meso-colic glands all deeply congested throughout their substance. 

Cover glass preparations from spleen pulp showed a large number of 
hog cholera bacteria. Cultures from the same revealed the presence of 
the same organisms only. 

INFECTION BY WAY OF THE LUNGS. 

It has been maintained by some observers that infection may take 
place through the lungs. Bacteria dried and carried about with the 
dust are supposed to be deposited in the lung tissue by the inspired 
air. It is of considerable importance to determine whether germs car- 
ried by currents of wind can in this way produce an outbreak at a dis- 
tance. There are two questions involved which must be dealt with 
separately in order to get as clear an idea as possible of this rather 
perplexing subject. (1) Do bacteria of hog cholera when inhaled pro- 
duce a disease which is similar to the disease described in these pages, 
i. c, without extensive lung lesions ; and (2) do hog cholera bacteria pro- 
duce a si)ecitic disease of the lungs when there deposited just as they 
produce intestinal disease when swallowed? Thefirst question, whethir 
the lungs may be considered an entrance of the virus when in the dried 
condition, is one for which not sufificieut proof is at present forthcom 
ing. Several experiments have been made at the experiment station 
to produce the disease by spraying pigs in a tight box with liquids con- 
taining hog cholera bacteria and by injecting them suspended in liquids 
into the trachea. In no instance was the disease produced. Several 
times bacteria were injected through the walls of the thorax into the 
pleural cavity and lung tissue without any result, excepting in two in- 
stances given on page 55. In one animal there was some pleuritis but no 
pneumonia. On the other hand the large intestine in this animal was 
severely diseased as in natural infection. In the other animal death 
occurred seven months after inoculation. The lung disease was most 
likely the comb'ned effect of lung worms and the mechanical injury re- 
sulting from the inoculation. 

If we must conclude, therefore, th;it animals are but rarely infected 
through healthy lungs, it is still less likely that tlu'S(> bacilli produce 
quite uniformly disease of the lungs, as i)as i een assumed by other ob- 



113 

servers without adequate proof. In the uotes of tbe outbreak ^iveu on 
page 54, this subject lias been pretty thoroughly discussed in the light 
of evidence furnished by bacteriological tests. The results there reached 
may be briefly summarized that lung disease or pneumonia of a severe 
character is not often found in hog cholera. The slight broncho-pneu- 
monia frequently met with is most probably due to. catarrhal conditions 
and to the aspiration of foreign bodies. There is, however, this very dis- 
eased condition of the lungs which may favor infection through tliem. 
When there are present foci of broncho pneumonia, hog cholera bacteria 
inhaled may lodge there, multiply in the secretion of the smaller bronchi, 
and cause an extension of tlie disease not jwssible in healthy lungs. 
From there they may be coughed up and swallowed, carried into the 
large intestine, where they exert their most destructive activity. In 
this sense the lungs may become the entrance of the virus, but only 
when previously diseased. In the examination of such diseased lobules 
of the lungs, in the outbreak referred to, hog cholera bacteria were found 
in almost exery case. In these case« it is difficult to decide whether 
they entered the diseased lobule from without by way of the bronchi — 
i. e.f with the air inspired — or whether they were deposited there by the 
circulating blood. 

The question of the relation of lung disease to hog cholera has been 
(;omplicated by the existence of an infectious pneumonia in swine, which 
we have called swine plague. This disease, which will be treated of 
in a special jjublication, appears over a large part of our country at 
times in virulent ei)izootics. It is caused by a widely distribute! septic 
organism, and ai)pears occasionally in swine suffering from hog cholera. 
In a number of such cases both disease germs have been obtained from 
the same animal. 

We do not exclude infection through the lungs as improbable in hog 
cholera, especially in epizootics characterized by more than usual viru- 
lence. At the same time long experience at the experiment station has 
shown that swine do not become infected in pens only a few hundred 
feet away from i)ens full of sick and dying animals. Currents of air 
can thus have but little power in distributing germs capable of inducing 
the disease. 

SOME OBSERVATIONS ON THE PATHOLOGICAL ACTION OF HOG- 
CHOLERA BACTERIA. 

We have frequently recurred to the fact that the intestinal tract seems 
to suffer more or less exclusively in hog cholera. The changes there 
produced belong chiefly to the necrotic and ulcerative' type, combined 
with a variable amount of neoplastic growth in tiie bottom of the ulcer. 
In connection with this work it has been impossible to nuike any ex- 
tended observations on the genesis of these ulcers owing to the exactions 
of other work. Whatever may be suggested here must be regarded 
simply in the light of inferences from lesions as they were observv^d 
post mortem. 

I06I2 H c- — 8 



114 

The ulcers are produced in most cases by a process beginning at the 
surface of the mucosa. This is shown very well by sections of ulcers 
in which only a portion of the tubular glands have been necrosed. 
What this process is must be left an open question. It seems very 
probable that the bacilli invade the tubules and blood vessels of the 
mucosa, by their rapid multiplication plug the latter, and cause a coagu- 
lation necrosis of the most superficial portion of the membrane. The 
various bacteria present in the intestine then complete the breaking 
down of the membrane, and an ulcer is formed. Ulcers may, however, 
be formed by bacteria carried thither by the blood, for ulcers are pres- 
ent in those animals upon which subcutaneous inoculation has been 
practiced (p. 110). In these cases the plugs or infectious emboli are 
situated probably in the submucosa. The resulting ulcer is deeper and 
more extensive. 

The formation of plugs or thrombi is confirmed by inoculations in 
rabbits (p. C9). The process of coagulation necrosis, as the result of 
plugs in the capillaries of the liver, may be seen in almost every case. 
Microscopic examiuation likewise reveals their growth in masses in the 
internal organs. 

The nature of the hemorrhagic ksions so frequently observed in hog 
cholera demands some attention. The rupture of minute and some- 
times larger blood vessels is no doubt due to the same process of throm- 
bosis and embolism in which the thrombi and emboli nuiy be made up 
more or less entirely of bacteria. Whether these i)lugs have a directly 
di'Structive action (necrosis) upon the delicate vascular wall so as to 
produce rupture and extravasation, as has been suggested in former 
reports, or whether the action is merely mechanical, or whether both 
causes are at work, it would be impossible to say. At* all events these 
hemorrhages are frequently the precursors of ulcers in the intestine, 
and in some cases the only lesions which were observed were hemor- 
rhages fiom large and small vessels. We may picture to ourselves the 
process, beginning, in most cases, with local ulceration in the large in- 
testine (cfEcum). The bacilli may be carried thence through injured 
vessels into other parts of the body, and to other portions of the iu- 
testine, where fresh ulcers may apx)ear; or the bacilli may be carried 
onward from the first ulcers to portions of the intestine lower down, 
where they again attack the mucous membrane. 

In many cases the quantity of virus introduced into the digestive 
tract is so great — as when pure cultures of hog cholera bacilli are fed — 
that destruction of the raucous membrane goes on at the same time 
throughout the csecum and colon, becoming less severe as the rectum is 
approached. The paralysis of the large intestine may cause extensive 
necrosis of the ileum. In these cases the action of the bacilli is purely 
superficial at first, penetrating deeper and finally reducing the entire 
wnil to a friable mass, greatly swollen by the infiltration of leucocytes. 
In such feeding experiments we may also observe gra<les of lesions as 



115 

we go away fi'oiii tbc valve in the ileum and in (lie colon. Instead of 
tbe conversion of the mucosa into a thickened, discolored, and roughened 
membrane, an amorphons, dirty grayish exudate may be found on it. 
The destruction, going on very slowly, causes a reactive inflammation, 
manifested by the exudate. 

The genesis of the intestinal lesions in the rabbit is somewhat differ- 
ent. They appear quite late in the disease as a result of the discharge 
of bacilli from the necrotic foci of the liver tissue into the bile duct. 
They are limited to the duodenum and large intestine, and are especially 
severe in the latter, forming there peculiar hnematomata or blood tu- 
mors, accompanied with a fibrinous exudate. The same lesions are 
obtained by feeding cultures. In view of this localization in the rabbit 
and pig we must admit that hogcholera bacilli exert their primary 
action where they are retained for a considerable time by the feces, 
and thus have an opportunity of multijilying before they attack the 
mucous membrane. 

The size of the spleen, sometimes enormous, seems to stand in no 
direct relation to the number of bacilli present. Sometimes a very 
highly congested spleen harbors only the average number of germs. 

The presence of hog cholera bacilli iu the lung- lesions met with in a 
small percentage of cases has already been dwelt upon (p. 51). The 
lesions themselves show nothing- characteristic. They are usually re- 
stricted to the most dependent lobe, the ventral on one or both sides, 
and to the writer they simply indicate a i)roneness of catarrhal inflam- 
mation in young- pigs, due, no doubt, to the aspiration of food and dirt, 
consequent occlusion of bronchi, atelectasis, and broncho pneumonia. 
The hog cholera bacilli which may be found here in most cases are present 
for the same reason that the}' are found in the spleen. Circulating in 
the blood, they find the contents of the diseased and plugged air tubes 
and alveoli a very suitable medium for multiplication. In this way they 
maj' add to the irritation and cause extension of the disease. 

It seems i)retty certain that the chiefdamage done b^' hog cholera bacilli 
lies in their power to grow in i^lugs in the small vessels. The 8im[)le 
reason why we have such severe lesions in the intestinal tract, although 
the bacilli arc present in small numbers in the internal organs also, lies 
in the anatomical nature of mucous membranes iu general and their 
ex[)oscd situation with reference to putrefactive processes. 

If the obscure action of these bacilli on cells and cell-life could be 
formulated at all, in the present state of our knowledge the writer 
would assume: 1. That they exercise a more mechanical influence by 
thrombosis, which leads, in the mucous membranes, to circumscribed 
necrosis. Death occurs not by the direct poisonous action of ptomaines, 
but from secondary causes, such as changes in the liver, septic infec- 
tion. 2. In acute cases the bacilli possess a greater power of invading 
the circulation. There they multiply rapidly enough to cause rupture 
of blood vessels in all the vital organs. Death may occur in these cases 



116 

by a ptomaine poi.soiiiiii;' of tbe nerve centers due to the large number 
of bacilli in the blood, or the loss of so much blood drawn from the 
circulation, or, what is more probable, by hemorrhages in the substance 
of the central nervous system. Whether this greater ability to invade 
the vital organs depends upon the production of a more poisonous pto- 
maine, which paralyzes opposing forces, or to other physiological prop- 
erties, belongs to the future for solution. 

Concerning the variation in the destructive nature of hog cholera 
bacilli little that is positive can be said. We have observed, for instance, 
that the disease dies out after a time in a herd, very frequently because 
there are no more animals left, or because the few that have survived 
have been exposed in such a way as to acquire immunity. But it has 
also been observed at the experiment station that the disease may dis- 
appear, even when fresh animals are exposed to it from time to time. 
The decline in virulence may be due to the particular season with its 
frosts or droughts, and other meteorological changes, or it may be due 
to a gradual weakening of the virus as it passes through the system of 
the exposed swine. W^e have observed several times that when a series 
of animals are fed with infected viscera, each from the one preceding it, 
the earlier ones of the series will develop the most severe disease. The 
later ones are aifected by a more chronic malady, and finally a point is 
reached when no disease is produced. In such an experiment self-inoc- 
ulation or vaccination must be eliminated, as the animals are not exposed 
previous to the feeding. But aside from this gradual dying out of par- 
ticular epizootics, we have noticed a difference in the outbreaks them- 
selves from year to year. In some the acute, hemoiihagic type would 
prevail, in others a more chronic ulcerative tyi)e. Such differences are 
most likely due to modifications of the disease germ itself, although here 
also it is difficult to eliminate differences in the animals due to race, 
feeding, cleanliness, etc., and differences due to the time of the year. 
As regards the manifestation of differences in the bacteria themselves 
none can be formulated. 

BACTEKIOLOGICAL INVESTIGATIONS OF HOG CHOLERA IN NEBRASKA, 
ILLINOIS, AND MARYLAND. 

The facts which have been gathered concerning the bacillus of hog 
cholera were obtained chiefly from epizootics occurring in the District 
of Columbia. The advantages of a bacteriological laboratory con- 
nected with the Bureau made investigations possible which could not 
be made in the field. It was, however, necessary to confirm the results 
already obtained by investigations elsewhere. These have led to the 
discovery of the same bacillus in Nebraska and subsequently in Illi- 
nois, thus identifying the disease in widely-separated localities. 

Ifebraska.— In March, 1886, the bacillus of hog cholera was isolated 
from one of ten spleens sent from Kansas and Nebraska. Tliough caie- 
fully removed by the inspector and placed in steiilized bottles i)lugged 



117 

with cotton wool, none came in good condition, owing to the long delay 
on the road. Small bits of spleen were placed under the skin of a num- 
ber of mice. Two which had been inoculated from the same spleen 
died of hog cholera. These experiments are reported in full in the Third 
Annual Eeport of the Bureau, and therefore need only to be summarized 
in this place. The bacillus obtained in a pure condition from these mice 
was carefully tested upon other mice, ui)on rabbits, and upon pigeons. 
The pathogenic effect was the same as that of the bacillus from eastern 
outbreaks. It was, however, readily observed that the Nebraska ba- 
cillus was less virulent, as it did not kill guinea pigs. A number of 
inoculation and feeding experiments were made upon pigs in order to 
produce the disease. All but two failed to show any disease. These 
two, fed with liquid cultures, were made ill, and one very sick was killed 
on the ninth day after feeding. The large intestine showed intense 
congestion, vith a few patches of adiptheritic membrane in theciBcum. 
No bacteria were obtained in cultures from the internal organs. This 
experiment, which was not very satisfactory, was repeated by feeding 
a larger quantity of culture liquid. The result was entirely satisfactory, 
as the following description of the experiment will show. Moreover, 
the feeding took pla^e nearly nine months after the microbe had been 
obtained originally from the spleen. During this time it had been cul- 
tivated in various media, passed through mice and rabbits, so that no 
trace of any spleen substance or foreign material could have been pres- 
ent in the culture liquid which was fed. The result also indicates that 
the pathogenic power of the bacillus was in grenfc part retained during 
this time. 

A flask containing between 500 and GOO cubic centimeters of sterile 
beef infusion was inoculated from a culture (rabbit), and after standing 
six days in the incubator the entire amount was given to a pig which 
had not been fed for thirty six hours. The culture liquid was covered 
with a thin membrane, and on microscopic examination contained only 
the motile bacillus. The animal became dull and weak, eating little. 
The bowels were loose on the fourth day. On the fifth it was unable 
to rise, and on the sixtii it was found dead. The autopsy notes are 
briefly as follows : 

In the abdominal cavity several hundred cubic centimeters of a red- 
dish serum, a thin translucent exudate covering the peritoneum of the 
intestine, which is diffusely reddened. Between the layers of the mesen- 
tery, along the line of attachment to small intestine, an abundant trans- 
lucent gelatinous exudate. Spleen very dark on section ; the surface 
dotted with elevated points of extravasated blood. Liver congested. 
Lungs normal, with exception of a few lobules, which are simply col- 
lapsed. 

Almost the entire digestive tract was found involved. Around the 
cardiac orifice of the stomach a zone of mucous membrane about 2 
inches in width was covered with whitish diphtheritic patches. Isolated 



118 

ulcers iu duodenum. Abont G or 7 feet of the lower portion of tbe 
small intestine very mucli thickened, the imicoas membrane covered 
Avith a thin sheet of necrosed tissue, whitish, brittle. The ctecum and 
portion of the colon greatly thickened and covered with a thick layer 
of necrosed tissue very rough and brownish. Near rectum necrosis 
gives way to closely set, isolated, roundish diphtheritic elevations of a 
whitish color, which leave a raw surface when scraped away. 

These lesions were, therefore, as intense as any produced by feeding- 
pure cultures of hog cholera bacteria obtained from the East. The spe- 
cific identity of the two bacteria from Nebraska and the East was thus 
completely established. 

In the liver and spleen the bacteria were few, for a cover- glass prep- 
aration from each organ did not show any after some searching. Liquid 
cultures from the blood (heart), spleen, and liver were turbid on the 
following day, and all contained the motile bacillus. Within four days 
complete membranes had formed on the surface. That the bacteria 
were very few in blood from the heart was indicated by a gelatine tube 
which had been inoculated several times with a platinum wire dipped in 
blood ; no colonies were visible on the fourth day. Of three liquid 
cultures, each inoculated with a loop of blood, two remained sterile. It 
was presumed that the liver would contain the largest number, inas- 
much as the portal circulation received its blood from the seat of the 
disease. This assumption was confirmed by the very abundant colonies 
surrounding a piece of liver tissue which had been dropped into a tube 
of nutrient gelatine. 

In order to make certain of the pathogenic i)Owers of the cultures 
obtained from this case of feeding the tube culture from the liver was 
used to infect two rabbits. The skin on the inner aspect of one thigh 
was carefully shorn and disinfected with .1 per cent, corrosive sublimate. 
An incision was made through the skin, and with a loop dipped in the 
surface growth of the culture a minute quantity was introduced into this 
pocket. The larger of the two rabbits was found dead on the fifth 
day. The lesions were briefly as follows: 

Slight amount of pus at the place of inoculation. Neighboring ingui- 
nal glands enlarged and infiltrated with blood. Surrounding vessels 
much injected and very tortuous. Liver very friable, spleen dark and 
enlarged; both dotted with points and stelhite spots of coagulation 
necrosis, especially numerous on tlie caudal surface of the liver. Both 
organs contained the bacteria of hog cholera in large numbers. Lungs 
hypostatic. A small number of ecchymoses beneath pleura; very few 
bacteria in kidneys and heart's blood. 

The second rabbit was found dead on the sixth day. The lesions 
were the same, if we except the more pronounced coagulation-necro- 
sis in the liver and its absence in the spleen. The bacteria of hog 
cholera were distributed as above; very abundant in spleen and liver ; 
lungs normal. 

Gelatine tube cultures from spleen and liver of these rabbits confirmed 
the microscopic examination. Liquid cultures from the blood contained 



119 

the motile bacteria, which hail lorined a brittle surface uiembraue ou 
tlie second clay. 

Diferential characters of the hog cholera bacillus from NchrasJxa. — The 
bacillus wheu staiued ou cover-glass preparations from the spleen and 
other viscera, closely resembles the one found in the disease prevalent 
in the East, so that it is impossible to distinguish them in this way. 

A few minor differences revealed in the various culture media indi- 
cated, however, that the two microbes were not alike in every way, and 
brought up the very interesting question of the variation of species 
of bacteria and the intluence of such variation ou the severity of epi- 
demics. 

The most noteworthy difference was observed in liquid cultures. 
Within twenty-four hours after inoculation from the spleen or blood the 
culture liquid became turbid, and upon its surface a complete membrane 
was present in nearly every case. This whitish membrane is not homo- 
geneous, but made nj) of patches of varying thickness, and when shaken 
slowly settles to the bottom in lumps and floceuli. The microbe of 
Eastern outbreaks does not form a membrane within several days after 
inoculation, and then only when the tube remains perfectly quiet. It 
appears as a whitish ring attached to the glass. 

In other respects the two microbes differed so little that no mention 
need be made of these differences here. We have, therefore, only the 
membrane 'on liquid cultures and a slightl}' diminished virulence, by 
which the bacilli from ]S"ebraska were distinguishable from those ob- 
tained from Eastern epizootics. Both of these characters are variable 
ones. The membrane can he produced in part b^' cultivating the East- 
ern germ for a long time at a high temperature. The variation in vir- 
ulence is observable during the course of almost every epizootic. 

Illinois. — From the spleen of an animal affected with hog cholera the 
specific bacillus was obtained during some investigations conducted in 
this State in the summer of 188G. The bacillus presented no diff'ernces 
whatever from the one obtained in Eastern outbreaks. Its effect upon 
rabbits aud mice was precisely the same. Its fatal effects when fed to 
a pig is well illustrated by the following experiuient: 

A pig was kept without food for over twenty-four hours. A 2i per 
cent, solution of sodium carbonate in meat broth was then given to 
it. Of this itconsumed aboutone liter, taking thus about'Jo grams of the 
salt. It was then fed with aboutoOcubic centimeters of gelatinecultures 
and 100 cubic centimeters of liquid cultures of the hog cholera bacillus 
obtained from rabbits which had succumbed to inoculation and from the 
original gelatine culture of the spleen made in Champaign County, 
111. The animal was found dead December 4, scarcely three days af- 
ter feeding. This was the briefest period of illness thus far observed. 
The lesions were very i)ronounced. Pyramids of kidne>s deep red 
throughout; glomeruli visible as dark points. Lungs pale, not fully 
collapsed. Right heart filled with semi-coagulated blood. Liver gorged 
with blood. Mucosa of stomach intensely reddened, especially along 
fundus, and covered with a thick layer of tenacious mucus. JNIucous 
membrane of ileum similarly affected. Peyer's patches exceedingly 



120 

dark red, showing tlirougli serous coat. Wlien viewed from tlie mu- 
cous surface tbe elevated border gives each a slightly concave boat- 
shaped appearance. The colon also deeply congested, almost hemor- 
rhagic in patches, filled with a small quantity of serai-liquid feces. The 
rectum still lilled with consistent masses. The mesenteric glands con- 
gested. 

The feeding had thus produced a very severe inflammation of the 
digestive tract. The diagnosis was further confirmed by obtaining pure 
li(iuid cultures from the spleen, the liver, and blood from the heart. The 
bacteria were not snfhcieutly numerous in these organs to be detected 
by the microscope. To make sure that the carbonate of soda had no 
corrosive effect, another animal was treated precisely in the same way 
by starving and feeding a solution of the salt. ISfoill effects whatever 
were manifested. 

In order to test the specific pathogenic character of the bacillus obtained 
from this animal a large rabbit was inoculated subcutaneously with about 
oueeight cubic centimeters of a liquid culture from the blood. On the 
sixth day the rabbit was lying on its side; abdominal breathing very 
labored. It was found dead on the next day. Slight thickening of the 
subcutaneous tissue and fascia covering the thigh muscles at the point 
of inoculation. The muscular tissue covered with minute ecchymoses 
around the infiltrated patch. Small quantity of serum in the i^eritoneal 
cavity. Spleen very large, blackish, exceedingly friable, and crowded 
with bacteria. Liver enlarged; interlobular tissue pale; the entire 
parencliyma very soft and brittle. Dotting both surfaces of all the 
lobes are small, grayish-white patches, involving one, two, or three, 
larely more, acini, and bounded very sharply by the acini themselves. 
I'eculiar figures are thus formed, three contiguous ones giving the 
l)atch a clover leaf appearance. On section they are found to extend 
to the depth of one or several acini into the parenchyma. The great ma- 
jority of these masses of coagulation necrosis involve lobules ou or near 
the surface. Only a few are in the depths of the organ. When such a 
whitish mass is spread on a cover-glass and stained innumerable bac- 
teria of hog cholera make their appearance. The rest of the tissue is 
likewise crowded Avith them. Beneath the inrlmouary pleura are large 
])urplish patches of extravasation, which ou section extend deeply into 
the parenchyma. The lung tissue is in general congested. Blood from 
the heart contained very few bacteria. No cultures were made. 

Maryland. — During September and October, 1888, an epizootic of hog 
cholera was started at the experiment station by a sick x>ig brought 
from near the city of Baltimore, Md. The hog cholera bacillus had been 
previously obtained from the spleens of two animals killed at Balti- 
more. At least twenty, which had been either simply exposed in pens 
or fed with the viscera of dead animals, saccumbed to the disease. In 
all cases pure cultures of the specific bacillus were obtained directly 
from the sj^leen. Its effect upon rabbits and mice, its appearance and 
mode of growth, did not differ from the bacillus as described in the fore- 
going pages, 

RELATION OF HOGr CHOLERA TO THE PUBLIC HEALTH. 

The importance of knowing whetber or not certain infectious animal 
liiseases have any deleterious influence upon human health, or are .the 



121 

direct cause of Imman disease, is not even second to the economic im- 
portance attacliing to aiiiaial diseases. There are some animal diseases, 
such as glanders, tuberculosis, anthrax, and rabies, which are directly 
communicable to man. This transmissibility was known before the 
si)ecific bacterial organisms of these diseases had been discovered. 
There are other animal diseases not proved to be transmissible to man, 
whose causes have only been definitely recognized within the past few 
years. As regards these it is quite pertinent to ask, in the light of 
l)resent knowledge, whether they have any relation to human diseases. 
Animal diseases when communicated to man may become so changed in 
character as to be unrecognizable. Hence we must determine whether 
the specific micro organisms of animal diseases are found in human dis- 
eases or not; in other words, whether the causes are identical. During 
the course of these investigations this problem has been constantly 
borne in mind. The question to be settled first has reference to the 
presence of hog cholera bacilli in human diseases. There are two mala- 
dies of mankind which resemble hog cholera in many respects— typhoid 
fever and dysentery. 

Typhoid fever is an infectious disease of man, prevalent throughout 
the civilized world, while hog cholera is known to exist only in North 
America and the British Isles, and during last year it has been identi- 
fied on the continent of Europe. Hence there could be no close relation- 
ship between the two diseases, for they would naturally occur together 
if they were identical. But there is another reason for their non iden- 
tity ; the uiicro-organisms which produce them are different. Thus the 
typhoid fever bacillus is a longer rod than the hog cholera bacillus, its 
movement in liquids is more sluggish and of a somewhat different char, 
acter. Its growth on boiled potato is almost pecnliar to itself. More- 
over, it has no pathogenic effect upon any animal thus far tried, and 
we know that the hog cholera bacillus is fatal to mice, rabbits, guinea. 
pigs, and pigeons after subcutaneous inoculation, and to pigs when fed 
to them. Hence there remains not the shadow of a doubt that genuine 
typhoid fever and hog cholera are distinct diseases. 

They do, however, belong to the same general class of infectious 
diseases. In both, infection very likely occurs chiefly through the food 
and drink. In both the lesions are ulcerative in character, located in 
the pig in the upper portion of the large intestine, in man in the lower 
portion of the small intestine. It is true the ulceration may be the 
secondary stage of processes primarily' diff"erent anatomically speaking, 
but we know as yet too little of the relative effect of irritants of the 
same kind, but of different intensity, to venture any positive statement. 
In both diseases the invasion of internal organs by the specific micro-or- 
ganisms takes place, so that they are readily obtained from the spleen. 
In both they appear in chimps or colonies in the capillaries. There is 
also a general resemblance of the two organisms, both as regards their 
appearance, motility and growth in various media when we compare 



122 

them with the bacteria of other infectious diseases in man and animals. 
We may tlierefore conclude that although these two diseases are en- 
tirely distinct there exists a close relationship between them as to the 
cause, the manner of infection, and the type of disease. 

Hog- cholera is allied to the disease or group of diseases known as 
dysentery even more closely than to typhoid fever. It resembles, per- 
ha ps, most nearly that form called epidemic dysentery. Of the causes of 
tliis disease very little is known. That the epidemic type is caused by 
microorganisms of some kind is now generally accepted, and it is also 
believed that there may be several distinct species of microorganisms 
which are capable of producing diphtheritic and ulcerative lesions of 
the large intestine.* Anatomically hog cholera and diphtheritic dys- 
entery are very much alike. The question whether hog cholera virus 
can ever produce a dysenteric afl'ection in man is not answered until we 
have learnt more of the causes of the latter disease. 

The danger, if any there be, of causing disease in man would only oc- 
cur upon farms where the opifortunity is afforded for infection of food 
and water by the discharge of diseased pigs. The preparation of pork 
by cooking is sufficient to destroy the bacilli if by any chance the flesh 
of diseased animals should get into the market. Experiments have 
shown that a temperature of 140° F. is sufficient for their certain de- 
struction. The temperature reached in boiling, roasting, etc., is of 
course mnch higher than this. 

In addition to these conclusions, which follow from the facts devel- 
oped by our experiments, it may be said that with the thousands of 
post-mortem examinations made by ourselves and other investigators, 
there has not been a single case where the operator became infected. 
In several instances it has been recorded that fresh wounds upon the 
hands have been covered with virulent material during the examinations 
without producing any appreciable effect. And through all the years 
that this disease has prevailed so extensively in the United States tbere 
has not been a case reported where it has been shown on good evidence 
to have been transmitted to the human species. 

Notwithstanding these facts, however, we should expect, with the 
prevailing carelessness in disposing of the carcasses of swine in many 
sections during such outbreaks, that there would be a more or less 
deleterious effect upon human health, not from the specific nature of 
the disease, but from the decomposing organic matter. Too often these 
carcasses are left to putrefy near dwellings, or are thrown into streams 
to contaminate them with decomposition products. Such practices are 
dangerous to the health of the community and should be prevented by 
the local sanitary officers. 

investigations of the Egyptian dysentery by Kocli a,utl Kartulis Lave shown that 
the cause is an organism helonging not to the class of bacteria, hut to the protozoa, 
and assuming the form of an amreba. This is ibund in hu-ge numbers in the ulcerated 
walls of the intestine. 



PREVENTION OF HOG CHOLERA. 

ISOLATION, DISINFECTION, AND CLEANLINESS AS PREYENTIYE MEAS- 
URES. 

It is frequently necessary to apply preventive measures before infec- 
tious diseases have actually appeared in a herd. The disease may have 
appeared on a neighboring farm, and the problem then arises : How can 
the infection be prevented from si)reading to other farms ? How can 
the surrounding farms keep the malady from their premises ? 

The sources and channels of infection are as follows, the most common 
and important being placed first : 

{(() Pigs purchased from infected herds, or coming in contact with those 
from infected farms, or running over grounds occupied by diseased sicine 
within two or three months. 

(b) Infected streams mag communicate the disease to herds below the 
source of infection. 

(c) Virus may be carried in feed, implements, and on the feet and cloth- 
ing of persons from infected herds and premises. 

{d) Winds, insects, birds {particularly buzzards), and various animals 
may transport hog cholera virus. 

{a) In regard to a, it may be said that no pigs should be purchased 
from any locality until one year after the death of the last case of chol- 
era. There are frequently near the end of an epizootic chronic cases 
which may live for three or four months without showing any distinc- 
tive signs of disease until they suddenly die. The post-mortem exam- 
ination usually reveals extensive ulceration of the large intestine. 
The disease may thus linger in a herd long after all danger has appar- 
ently subsided. By bringing any chronic cases in contact with hitherto 
unexposed healthy swine the disease may spring up anew, as a dying fire 
Avould when supplied with fresh fuel. Although our experiments have 
shown that the disease germs may all disappear from the soil in three or 
four months, the uncertainty of knowing whether there are any chronic 
cases continually adding fresh virus to the soil makes the period of one 
year not too long to avoid the introduction of unexposed pigs. It is 
advisable, in districts where hog cholera is very prevalent and is rarely 
absent for any length of time, for farmers to raise their own pigs and 
not trust to any animals from outside. In this way infection may 
be at least in part kept under control. When animals have been ob- 
tained from i)laces which are not above suspicion they should not be 
brought in contact with swine already on the place, but quarantined as 

123 



124 

far as possible from them aud kept under careful observation for at 
least one mouth. 

(b) Perhaps the most potent agents in the distribution of hog cholera 
are streams. They may become infected with the specific germs when 
sick animals are permitted to go into them or when dead animals or 
any part of them aie thrown into the water. They may even multiply 
when the water is contaminated with fecal discharges or other organic 
matter. Experiments in the laboratory (p. 70) have demonstrated that 
hog cholera bacilli may remain alive in water for four months. Making 
all due allowance for external influences and competition with other 
bacteria in natural waters, we are forced to assume that they may live 
at least a montli in streams. This would be time enough to infect every 
herd along its course. 

(c) Hog cholera germs are not immediately destroyed by drying. 
Laboratory experiments show that they may retain their vitality from 
two to four months. Hence it is not difficult to see how a person walk- 
ing on infected ground and among infected animals may carry on his 
shoes and clothing dried germs of the disease to any neighboring herd. 
For the same reason hog cholera germs may be carried from infected 
grounds to others by fe^d, and by farming implements which have come 
in contact with infected ground. 

{il) There is no reason to suppose that currents of air have much in- 
fluence in spreading the disease. Observations at the experiment sta- 
tion of the Bureau have left no doubt that healthy pigs may be kept on 
the same farm with diseased ones without becoming infected, provided 
the infection is not carried in feed and implements, or on the shoes and 
clothing of persons from the sick to the healthy. Moreover the disease 
is an intestinal malady, and all evidence points to infection through 
the food rather than through the air inspired. 

The agency of flies and other insects is perhaps equally limited when 
infection is to be carried from one place to another. Our experiments 
show very well that the sting or bite of an insect is not sufficient to pro- 
duce the disease. It is possible, however, that they may carry the 
virus from one place to another in the same yard. This will be dis- 
cussed more fully under another head. 

The agency of buzzards in distributing the disease in the Southern 
States seems probable, although there is no positive proof. These birds 
will readily consume carcasses of dead swine. If the hog cholera germs 
are not destroyed by digestion it is reasonable to assume that the feces 
contain the living germs, which may cause the disease to break out at 
some distant place. Of course, the remedy would be to immediately 
destroy or bury dead animals. 

There is some reason to believe that rats, dogs, aud perhaps other 
small animals may carry the germs upon their feet or in their hair and 
thus infect premises. It is probable that the contagion is only rarely 
transported in this manner, but there are outbreaks the origin of which 



125 

it is difficult to exi)laiii otheiwise. We uuiy readily conceive, bear- 
ing in mind the facts enumerated above, bow sucli auimals might be- 
come contaminated with moist, semi-liquid, or liquid matters containing 
the germs, and that these substances drying upon the feet or hair would 
adhere for a considerable time. If an animal thus infected should go 
into uninfected lots occupied by swine and deposit there the smallest 
l^article of the germ containing material, either in liquids standing in 
the feeding troughs or in moist organic matters suitable for the multi- 
plication of the microbes, an outbreak of the greatest virulence might 
be set up. The number of conditions which must coincide for the spread 
of the disease in this way probably accounts for the comparative rare- 
ness of this kind of infection. 

Granted, tlien, no communication between infected and uninfected 
farms, there still remains the danger of infected watercourses, upon 
whicli it is impossible to lay too much emphasis. In fact, if the disease 
exists anywhere along a stream all farms below that point are liable to 
infection unless use of the water in any form whatever is given up dur- 
ing the season. 

By paying particular attention to these points, there is no doubt that 
the disease can be warded off, even when in the immediate neighbor- 
hood. Hog cholera is analogous to typhoid fever, dysentery, and Asiatic 
cholera in man in many particulars, and there is a quite unanimous 
opinion that these diseases are most commonly transmitted through 
drinking water. The same may be predicated of hog cholera, ajid the 
mysterious spreadof tliis plague will no doubt frequently be understood 
by examining the water courses. 

When the disease is in the neighborhood it has been customary with 
some to feed swine on some so-called " preventive" medicine. These 
arc frequently prepared or invented by individuals who Lave little, if 
any, knowledge of the action of medicines. The outcome is that the 
animals fed with these unknown compounds are not only not benefited, 
but their vitality is af;tually reduced, and when the disease appears it 
destroys the weakened animals much more easily. The writer has made 
post-mortem examinations of several animals in the West where such 
preliminary treatment was going on, and the peculiar changes of the 
internal, organs, not like any known disease, could only be referred to 
the action of such preparations. It must be remembered that there are 
few medicines which are not injurious or poisonous in large doses* 
They should not be used thus excepting under special conditions, and 
only given as recommended by those who have been trained to know 
the peculiar value and effect of drugs. 

The condition of the animals themselves is of great importance in 
favoring ur preventing infection. When pigs are fed with liquids in 
which the specific bacilli only are present, those that have been de- 
prived of food for some time previous take the disease, while those 
v;hose stomachs contain food that is undergoing digestion do not take it 



126 

readily. If, besidr.'s starving tlie animals, they are fed witli some alka- 
line solution, by which the alkalinity of the stomach is increased, the pa- 
thogenic effect is still more pronounced. Any disorder of digestion by 
winch the secretion of gastric juice is diminished or checked and the 
mucus is increased in quantity will increase the susceptibility of the 
animal to infection, because the alkalinity of the mucus mIU favor 
rather than destroy the virus. Any mode of feeding which produces 
constipation and over-distension of the large intestine is likely to favor 
the disease, as the virus is retained for a longer time. During epizootics, 
therefore, besides the preventive measures suggested, the animals 
should be carefully fed upon food which tends to keep the bowels open 
and the feces soft, and which does not interfere with normal digestion. 

When there is a suspicion that a herd has been infected, although 
the disease has not yet appeared, disinfection, and all the rules laid 
down' below (p. 130) should be carried out with great care, as if the dis- 
ease were actually present. 

When hog cholera has appeared in a herd or on a farm, precautions 
should be taken for two reasons: (1) To jirevent the virus from being 
carried to other farms and infect other herds. (2) To prevent the loss 
of the entire herd, or, if this is not possible, to stamp out the disease in 
such a way that the ground shall not infect healthy animals subse- 
quently. 

The rules under the first head should be prescribed by law to protect 
l)roperty frotn the consequences of the carelessness or the willfulness 
of those who refuse to take proper precautions. They may be summar- 
ized as follows : 

(a) The dead animals should be immediatehj disposed> of^ cither by burial 
or by burning^ or if ihey arc talcen to some rendering establishment their 
transportation should be gorerned by well-defined rules which will prevent 
the dissemination of virus on roads, in wagons, cars, etc. 

{b) Streams should be carefully protected from pollution. 

(c) No animals should be removed from any infected herd or locality to 
another free from the disease for at least six months after the last case of 
disease. 

{a) The proper disposal of dead animals is a matter of great impor- 
tance, for the bodies not only contain the germs of the disease, but the 
latter will multiply enormously during summer heat in the internal or- 
gans after life has been extinguished. Each dead body must therefore 
be regarded as a focus of the disease unless properly disposed of. It 
may be buried. In such case it must be so deep that no animal can get 
at it. It should be covered by a layer of powdered or slaked lime sev- 
eral inches thick, and the ground over the body likewise sprinkled with 
a thin layer of the same. If the carcasses are burnt, care should be 
taken that any parts not consumed are buried as directed. If they are 
carried away some distance to rendering establishments, at best a dan- 
gerous pocedure, employes of such establishnieiits should be compelled 



127 

to wrap arouiiu the carcasses impervious cloths wetted with a 2 per ceut. 
solution of carbolic acid, so as to protect the roads from the virulent 
drippings. 

[b] The danger from infected streams has already been mentioned at 
length. These must be protected by law iu such a way that no sick ani- 
mals should be allowed to go near them, and that no carcasses be thrown 
into them or deposited where drainage may carry the virus from the 
body into the water. Nor should the drainage from pens be permitted 
to flow into them. 

(c") Hogs are frequently affected with cholera of a mild form, which 
lasts for several months before some form of septic infection or degen- 
erative changes in the internal organs produce death ; hence it is im- 
portant to insist upon knowing when the last case of disease occurred. 
Since it hits been demonstrated that hog cholera germs may remain 
alive iu the soil from three to four mouths, this rule will not appear un- 
reasonable as a safeguard. 

These rules will be sufficient, if properly executed, to confine the 
disease within narrow limits. There is no doubt that hog cholera virus 
dies out over the greater part of our country after epizootics have swe[»t 
over it. We have no reason to believe that it can survive iu the soil 
from one end of the year to the other. It is, in fact, highly probable 
that it is transported and distributed from a few places where, for some 
reason, cases have occurred throughout the year and have thus kept 
the vii'us alive. There are no experiments on record which show that 
the hog cholera germ may be found in the soil and water independent 
of the disease. It has been looked for, but has never been found, ex- 
cepting in the body or discharges of diseased swine. 

In view of the fact that the disease can be kept under control, the 
legislatures of those States which suffer most severely from this plague 
should take steps to enact rules similar to those formulated above. 
The States of Kansas and Nebraska have on their statute-books laws 
of this character, which read as follows: 

AN ACT to prevent the spread of disease among swine. 

Be it enacted by the ler/islature of the Slate of Kansas, It is hereby made the duty of 
every person who owns or who has the control of any hog that has died of any dis- 
ease to bury or burn the same within twenty-four hours after such hog has died, and 
any person who knowingly fails or Refuses to comply with the provisions of this sec- 
tion shall be deemed guilty of a misdemeanor, and upon conviction thereof shall bo 
fiucd not exceeding one hundred dollars. 

Sec. 2. Whoever shall knowingly barter or sell any hog afflicted with any disease 
without giving full information concerning said disease sliall be deemed guilty of a 
misdemeanor, and upon conviction thereof shall bo fined not exceeding one hundred 
<Ii)Ilars. 

Sec. 3. Whoever shall knowingly barter or sell any hog which has died of any dis- 
ease shall be deemed guilty of a misdemeanor, and npon conviction thereof shall be 
fined not exceeding one hundred dollars. 

Sec. 4. Whoever shall throw or deposit a dead hog in any river, stream, creek, or 
ravine shall be deemed guilty of a misdemeanor, and upon conviction thereof shajl 
,bo fined not exceeding one hundred dollars. 



128 

AN ACT to preveut tbo spread of hog clmlera ami other liiiidred diseases, aud prevent trafKc iu an- 
imals dying from infectious or other diseases. 

Be il enacted bij the Ivglslalurc of the Slate of Xehraska, That it shall be the duty ol' 
the owuers of swine or other domestic animals dying from cholera or other diseas<'s, 
within twenty-fonr hours after their death, to cause the carcasses of such animals to 
be suitably buried or burned up ou the premises owned or occupied by such person. 

Sec. 2. If the owner of any swine or other domestic animals dying from cholera or 
other disease, or any other person, shall sell or dispose of the carcass of such swiue or 
other domestic animals, to auy person for the purpose of niauufacturiug the same into 
soap or rendering the same into lard, or for other purposes, or if any person shall buy 
or otherwise obtain the carcass of any swiuo or other domestic animals, dying from 
cholera or other disease, for manufacturing purposes as aforesaid, or any other i)ur- 
pose except that of burial or burning, as provided in the preceding section, every 
such person shall upon conviction be lined in any sum not less than twenty-livo dol- 
lars nor more than one hundred dollars, or be imprisoned not exceeding six months. 

Sec. 3. Whereas an emergency exists, this act shall be iu force and ta.ke effect from 
ami after its passage. 

Approved, March 4, 1885. 

These laws, although not sufficieutly explicit, touch upou the most 
importaut points, and are important movements in the right direction. 
We would suggest laws embodying the three heads in their entirety as 
given above under ff, Z>, and c, together with directions for their proper 
execution. The disease, spreading so easily and rapidly, requires great 
promptness of action and quite different rules from those which must be 
adopted iu the suppression of glanders or tuberculosis, for example. 
The difference is due to the nature of the specific microbe, so unlike 
those causing the two diseases mentioned. 

It is not strange that so little attention has been paid to the restric 
tion of this disease in the past, since legislators and boards of health 
and State veterinarians have had no scientific basis upon which to 
frame laws. Even now efforts are being made in varioas^ quarters to 
controvert or openly deny the accuracy of the investigations and re- 
sults obtained by the Bureau, and throw the whole subject back into 
the chaos iu which it was but a few years ago. This must have any 
thing but a salutary eifect upon those intrusted with the framing and 
execution of specific laws for the protection of domesticated animals. 

Having thus far dwelt upou the means which must be adopted to 
prevent the spread of the disease from one place to another, it becomes 
necessary to consider someof tlie measures that should be employed in 
checking it after it has once taken foothold in a herd. But how are 
we to recognize the disease? To answer this question it may be well 
to recai)itulate briefly some of the more important features of the mal- 
ady in as simple language as possible: 

It is quite common for the disease to announce itself by a few sudden 
deaths. The stricken animals may seem well a day, perhaps only a few 
hours, before death. In order to remove any doubts as to the precise 
nature of the disease, it is best to examine one or more of the animals 
before burying or burning them. This should be done in a secluded 



129 

place which pigs can not reacb, and the ground thoroughly disinfected, 
as will be described later. The disease in the sudden cases can be 
easily recognized. The spleen is, as a rule, ver^' black and enlarged. 
Spots of blood from the size of a i)in's head to a quarter inch or more 
will be seen in the fat under the skin, on the intestines, lungs, heart, 
and kidneys. The lymphatic glands are purplish instead of a pale pink. 
When the largo intestines are opened they are found covered with these 
dark spots of blood more or less uniformly and entirely. Often the 
contents are covered with clotted blood. Any or all of these may be 
considered as signs of the disease in its most virulent form. In many 
outbreaks the early cases do not succumb so rapidly. They grow weaker, 
lie down much of the time, eat but little, and usually have diarrhea. 
Most of such cases maj^ linger for weeks, meanwhile scattering the 
poison in the discharges. The disease may be recognized in these cases 
as soon as they are observed to act suspiciously, and there should be 
no delay in determining at once the nature of the disease. When the 
animal has been opened the large intestine should be carefully slit up 
and examined, beginning with the blind or upper end. There will be 
seen roundish, yellow or blackish spots, having an irregular, depressed, 
sometimes elevated surface. These spots correspond to dead portions 
of the mucous membrane, and they are frequently seen from the out- 
side as soon as the animal is opened. Sometimes the membrane has 
been entirely destroyed. (See also pp. 39-52.) 

In order to comprehend fully the reasons for the preventive measures 
suggested, let us briefly trace the various ways in which hog cholera 
bacteria may pass from a diseased or dead animal to a health^' one. 

Pigs may become directly infected by feeding on the carcasses of such 
as have died of the disease, or by eating food contaminated with the 
feces and urine of sick animals, or they may become indirectly infected 
by feeding upon material in which hog cholera bacteria are accidentally 
])resent, and in which they have multiplied. This would include milk^ 
water, and perhaps most vegetables in a boiled condition. It has been 
pointed out in i:>receding pages that hog cholera bacteria multiply very 
abundantly in milk, especially in warm weather, that they remain alive 
in water for months, and that they multiply upon boiled potato. It 
has also been shown by an extended series of experiments (p. 80) that 
they may remain alive in the soil for from one to four mouths. The 
sources of infection are thus numerous enough. It has likewise been 
demonstrated that these disease germs will resist drying. Hence, dried 
discharges of the sick or the dried body of dead animals are still in- 
fectious. 

The channel of iufection is in most cases the food and drink. This 
has been frequently demonstrated and emphasized in these pages. 

The food, after leaving the stomach, passes in a liquid condition 
through the small intestine, so that this never seems filled; in fact, its 
only contents are a coating of semi-liquid matter over the mucous mem- 
15G12 n c 9 



130 

braue. It pas^ses tbiougb the small intestine quite rapidly, but on 
reaching- the large intestine the undigested remains become more con- 
sistent, because the liquid is re-absorbed, and are kept here for some 
time. The bacteria, if not destroyed by the gastric juice, pass quickly 
through the small intestine, but in the large intestine they begin to 
multiply and attack the mucous membrane, which they destroy. Thus 
the feces or discharges of diseased pigs, wherever deposited, scatter 
larger or smaller quantities of the virus in this way, completing the 
circle of infection. 

In order to prevent the remaining healthy animals in an infected 
herd from takiug the disease the following measures are suggested as of 
importance, some or all of which may be carried out according to cir- 
cumstances : 

{a) Removal of still healthy animals to inclosed uninfected ground or 
pens, as far as possible from infected localities. 

(b) Destruction of all diseased animals. 

(c) Careful burial or burning of carcasses. 

(d) Repeated thorough disinfection of the infected premises. 

(c) Great cleanliness, both as to surroundings and as regards the food, 
to prevent its becoming infected. 

(rt) The importance of this measure need not bo insisted upon, after 
what has been stated of the various ways in which pigs may bo infected. 
The distance to which they may be removed will, of course, depend on 
circumstances. They should be kept so far away that there can be no 
means of communication, eitlier by direct contact, by drainage of the 
surface of the soil, or by gusts of wind. They should not be kept too 
closely confined, for if the disease should have attacked one or more 
and not manifested itself before removal, the infection would become 
general. Even after this precaution is taken, latent disease among such 
as are apparently healthy may infect the new grounds and the remain- 
ing healthy animals. This danger is increased by the fact that not un- 
frequently a number of animals become infected from the same source 
at the same time. Some will show symptoms very speedily ; in others 
the disease will remain latent for a longer time. Under such circum- 
stances it is impossible to properly isolate the well from the sick. Then 
there is the difficulty of preventing the well animals from carrying the 
virus on the skin and feet into their new quarters. These drawbacks 
may be in part overcome by very promjit action when the first signs of 
disease appear in a herd, before the virus has had an opportunity of 
being scattered about. The bodies of those to be removed may be 
fairly well disinfected by pouring over them a 2 per cent, solution of 
carbolic acid, and forcing them to walk through such a solution. 

(b) This measure is recommended to prevent the further spread of 
the virus by the diseased animals. In view of the fact that few re- 
cover, that even these few are stunted and of little value, that there is 
no reliable means of treatment which will eventually cure, destruction of 



131 

all sick aiiiimils is tlie simplest uiul most economical inocedure in the 
end. 

((•) The (lisi)()sal of carcasses has alrea'iy been discnssed (i). ll*8). 
This very important measure should never be lost sight of. 

{(1) Among the various disinfectants which can be recommended are 
the following: 

No. 1. Slaked or unslaked lime, used both as a powder and as slaked 
lime, containing about 5 to 10 per cent, of dry lime (from i to 1 pound 
of lime to a gallon of water). 

iSTo. 2. Crude carbolic acid, i^repared by adding to the crude carbolic 
acid obtainable from druggists at about 90 cents a gallon an equal 
quantity of ordinary sulphuric acid. This mixture is to be carefully 
added to water in the i)roportion of 2 ounces to 1 gallon of water, about 
]^ per cent. A'olume (see p. 91). 

iSTo. 3. A 1 per cent, solution (volume) of ordinary sulphuric acid (^ 
ounces of the acid to 1 gallon of water). 

No. 4. A 2 per cent, solution of pure carbolic acid. This is prepared 
by heating the crystals slightl}' until they melt and adding the resulting 
liquid to hot water, in the proportion of 1,^ ounces to half a gallon of 
water. (A pound of carbolic acid, crystallized, retails at 55 cents.) 

No. 5. Boiling water. 

The careful laboratory experiments with these disinfectants, upon 
which their practical application is based, are given on p. 87. We shall 
confine ourselves in this place to a description of their employment. 

Disinfectants are substances which, in solutions of a certain strength, 
are capable of destroying disease germs. Consequently they should be 
applied wherever the disease germs are supposed to be. In case of hog 
cholera they are attached to the sides and floorings of pens and to the 
various utensils used in cleaning them. They arc mixed with the earth 
over which the diseased animals have run, or in the water which they 
have frequented. In the report of the Department for 188G the use of 
mercuric chloride (corrosive sublimate) was recommended, as it is a pow- 
erful disinfectant. Since that time other disinfectants have been tested 
which are equally cheap and easily procurable. The main objection to 
mercuric chloride is its extremely poisonous character, which makes it 
undesirable to deal with. This substance has, therefore, in spite of its 
powerful germicide properties, been thrown out of our list of available 
disinfectants. 

The wood- work of pens, fences, flooring, etc , is best disinfected by 
using upon it, with a broom, solution No. 2 until thoroughly wet. In 
preparing this solution it should be stated that the mixing must be 
done in a glass bottle or jar and the mixture poured slowly into the 
proper amount of water in a wooden pail. This should be rinsed out 
after using to jirevent the acid from slowly destroying the iron hoops. 

Whenever No. 2 is not obtainable No. 3, which seems to be equally 
efficient, may be used in its place. 



132 

Lime is a very efficient disinfectaut for hog cholera. Experiments 
have shown (p. 93) that a solution containing only .02 per cent, will de- 
stroy the bacteria. When much organic matter is present, as nuich as 
.5 per cent, to 1 per cent, may be necessary. We recommend the pro- 
portions given under No. 1, which give from 10 to 20 times the strength 
required. The resulting liquid is not too thick to be easily manipulated 
It may be used on wood-work as a whitewash, and it may be spread as 
a thin layer over the soil which has been infected. 

The 2 per cent, solution of pure carbolic acid should be used when- 
ever No. 2 ma3^ act injuriously by virtue of the sulphuric acid which it 
contains. 

In general we recommend the use of No. 2 or No. 3 as often as it maj^ 
heem necessary. It should be dashed upon the infected pens, troughs, 
tools, and over the infected soil. Wheu there is no objection to lime 
this may be used on the soil, as it is equally efficient. The discharges 
should be covered with powdered or slaked lime, and this should be 
thrown in abundance into pools or wherever water stagnates. In the 
case of troughs for feed, iron tools, etc., which are liable to injury, the 
disinfectaiit should be washed away with boiling water if this is at hand. 
Boiling "water will destroy hog cholera germs by simple contact, and 
the disinfection will thus be made more complete. Shoes may be dis- 
infected b.\ rubbing them with solution No. 4. 

It must be carefully borne in mind that no manure from sick i)igs 
should be removed until it has been treated with disinfectants. The 
cleaning must be done after disinfection and not before, to prevent the 
dissemination of living virus. 

The agency of mice and rats in transporting virus will dej)end upon 
the promptness and thoroughness with which disinfection and cleanli- 
ness are practiced. Mice are more dangerous than rats, in so far as 
they may take the disease by feeding (p. 72). Flies can cnly carry 
such small quantities of the virus that they are not likely to prove dan- 
gerous if disinfection and cleaning of feed troughs are attended to. 

If these measures are carefully carried out, the disease may either be 
checked or else mild cases only will appear, owing to the small quantity 
of poison which the animals are likely to consume with the food. 

The epizootic may be terminated by the destruction of most of the 
herd. This unfortunately is usually the case. What x)recautions must 
be taken to prevent subsequent outbreaks'? 

If only a few animals remain, it is best to slaughter thehij they are 
likely to suffer with the disease in a mild form and continue to infect 
the premises. If no more animals remain, there should be a tinal 
thorough disinfection and subsequent cleaning of the whole exposed 
teriitory, including every nook or corner where the disease has existed. 
This should be done with solution No. 2 or No. 3 as directed, used as 
freely as possible. After one or two days the ground may be covered 
with a thin layer, one eighth inch or more, of slaked lime in the strength 



133 

above given and left undisturbed. If there is no objection to wliitewasb, 
tbir, may be applied to infected woodwork as an additional safeguard. 
Even after this thorough treatmeut, it is best not to place any fresh pigs 
on the premises for at least four months after the final disinfection. 
When animals still remain that have been exposed and have not taken 
the disease, no fresh animals should be introduced for at least six mouths 
after the termination of the outbreak. The disinfection must have been 
equally thorough. 

After all this trouble has been taken there is still remaining the dan- 
ger of a fresh introduction of the disease, and we would therefore again 
call attention to the rules laid down in tlie beginning of this chapter. 
These, after all, must be considered as most important. It is much easier 
to keep the disease away than to eradicate it after it has been intro- 
duced, without great loss of time and money. We would also suggest 
that in those regions where the danger from hog cholera epizootics is 
always present, the methods of keeping hogs be simplified in such a 
way that disinfection may be practiced without too much labor and un- 
certainty as to the results. It is only necessary to visit a few farms to 
be convinced of the difficulty that may be met with in endeavoring to 
eradicate the disease. The hogs are allowed to stray into the most 
out of the-way places when sick instead of being kept in inclosures of 
definite form and size, which are readily nccessiblo. The poison is thus 
scattered in such a wa^' as to make disinfection impossible. It is cer- 
tainly not necessary in raising pigs to allow them to stray into arbors, 
behind hedges, hide themselves under barns and outhouses. In some 
farms which we have visited, and which were said to have hog diseases 
most of tlie year, there seemed to be no places about the house or gar- 
den where pigs did not go. Under such circumstances disinfection is 
is quite impossible. The pens and other wooden structures, fences, etc., 
are also apt to be in a very dilapidated condition, so that cleaning is 
very much complicated. Even under such circumstances the germs will 
finally perish without disinfection if enough time be given, since they 
gradually die in the soil and water, as our experiments have shown. A 
period of from six to nine months after all animals have been removed 
will be, in general, sufficient to purify the soil of these disease germs. 
In fact the natural disinfection is very probably accomplished in many 
cases in from three to four months, but it would not be safe to rely upon 
this. 



TREATMENT OF HOG CHOLERA. 

Upon tbio subject very little sboiild be said, for the reason tbat dis 
eased animals are a source of poison aud a menace to bealtby animals, 
and sbould be destroyed. Moreover treatment is exceedingly unsatis- 
factory, as tbe disease either terminates fatally, whatever remedies are 
used, or generally makes the animal useless if it sbould recover. We 
therefore urgently recommend slaughter of the sick aud thorough dis- 
infection as the safest and most economical treatment in the end. 

Treatment, however, is resorted to by a large number of owners of 
swine. Tbe number of specifics, so-called, which are being advertised 
is legion. We have tried some of the best recommended and found them 
of no avail. ISTor is there any "specific" known in the range of veter- 
inary or human medicine that will cure diphtheritic and ulcerative dis- 
ease of the large bowels except time, combined with ciirefiil dieting, 
rest, and a few palliatives to relieve pain. It is impossible to carry out 
this treatment on swine. The success frequently reported with sp^v 
cities iu hog cholera are very probabl3' due to the fact that the tieat- 
mentis usually adopted in mild forms of disease of a different nature 
which is mistaken for cholera, or when the acute outbreak is over and 
the plague has assumed a chronic character. The affected swine linger 
for a time with very slight symptoms of disease, and this change is 
credited to tlie "specific" employed. Remembering that the severest 
injury is done to the walls of the large intestines in this disease, we 
regarded it important to determine what medicine would give a prompt 
ami copious evacuation of the bowels in the very beginning of the dis- 
ease. Various medicines wtre tried by Dr. Kilborne, at the Experiment 
Station, among others the following: 

(1) Calomel and jalap.—Fehruixry 20, 1888. To No. 4G3, 30 grains 
calomel ; to Xo. 407, 23 grains jalap; to No. 4(38, 30 grains each of cal- 
omel and jalap. February 21. Same dose given again to Nos. 403 
aud 408; no result. 

(2) Calomel. — March 7. To Nos. 441 and 442, each one dram of dry 
calomel. March 8. To 441 same dose mixed with castor oil; to 442 
about li drams with castor-oil. No. 441 was freely purged after second 
dose, continuing for twenty to thirty-six hours. No.- 442 was freely 
purged after sixteen hours, continuing sixteen to twenty hour-j, when 
it died. At autopsy were found intense intiammation of stomach, super- 
ficial necrosis of the mucosa of large intestine with deep reddening 
resembling hog cholera. No bacteria found in cultures Irom spleen. 
These changes were no doubt due to the calomel. 

135 



136 

(3) Calomel. — March 8. Nos. 403 and 4G8 received each one dram 
Coloniel in 2 drams castor-oil. No. 408 was purged freely in twenty 
hours, continuing- thirty six hours. No. 403 was purged in sixteen 
hours and made ill for several days. 

(4) Epsom salts. — Nos. 403 and 405 (w^eight 50 pounds) received each 
1 ounce. Bowels slightly relaxed for one or two passages. Nos. 339 
and 377 (weight 50 jiounds) received each 2 ounces in water. No. 339 
Avas purged and made slightly ill. No effect on 377. 

(5) Barhadoes aloes. — Nos. 402 and 404 (weight 50 pounds) receiv^ed 
one-half dram each; no effect. Nos. 372 and 380 (weight 05 i:)Ounds) 
received each 2 drams, mixed in molasses ; no effect. The same ani- 
mals, five days later, received each 4 drams with molasses; no effect, 
except discoloration of feces. 

(0) Castor-oil and turpentine. — Nos. 387 and 388 (weight 50 to GO 
pounds) received each If, ounces castor-oil and one sixth ounce turpen- 
tine ; no effect. No 387 received, five days later, 2^ ounces oil and one- 
sixth ounce turpentine. No. 388 received, five days later, 2^^ ounces oil 
and one-third ounce turpentine; no effect. 

(7) Linseed-oil and turpentine. — Nos. 383 and 399 (weight 50 to 60 
pounds) received each 2i ounces oil and one sixth ounce turpentine ; 
no effect. No. 383 received, five days later, 4 ounces oil and one-sixth 
ounce turpentine. No. 399 received five days later, 4 ounces oil and one- 
third ounce turpentine. Both were made sick for a day or two. No 
catharsis. 

These trials show how difficult it is to cause movement of the large 
bowels in swine, and they also suggest that this very sluggishness may 
make them susceptible to inflammations and ulcerations such as we 
find in nog cholera and frequently in swine plague. 

It was our intention to obtain a cathartic which would freely purge 
without causing any inflammation or irritation of the large intestine. 
Of those tried, calomel is the only available one. This must be carefully 
given, as it may produce the very inflammations which it is designed to 
check, and destroy life, as was acttmlly done in experiment 2. 

Concerning calomel EUenberger* says: 

Calomel (in combinatiou with castor-oil) is especially serviceable with swine; with 
larger animaLs Avheu the cont(!nls of the intestinal canal are to be disinfected, and in 
inflaminatory fevers. It shonhl be given to ruminants with the greatest cantion. 

It\vas our purpose to try calomel after having made these trials upon 
healthy aninnils, when the disease died out at the Experiment Station, 
and further investigations had to be postponed. 

If the large intestine has been promptly evacuated the next important 
step is to give only that food which leaves but little irritating waste to 
pass into the large bowel, sucli as milk and gruels. In short, it is best 
to use only boiled or scalded food so as to help the process of digestion 
as much as possible. It may be necessary to repeat the dose of calo- 
mel after a few daj^s. As to this mode of treatment our experience is 
not sufficient to warrant any positive statements, and it is simply sug- 
gested to those who wish to run the risk of treating this disease. 
* Lehrhiich d. aUtjemdiieii Tlierapie d. Ha used iigeth here, indf), p. 676. 



137 

There is another line of preventive and cnrative treatment which may 
prove valuable in the future, namely, the feeding of substances with the 
daily food which, while not injurious to the animal itself, may keep in 
check the multiplication of the virus in the intestine by an antiseptic 
action. It is very imi)ortant, however, to bear in mind that a large 
number of those medicines which act as disinfectants and antiseptics 
are likewise injurious or even poisonous to the animal itself. A too 
abundant feeding of such material, while it may reduce the mortality 
and lessen the severity of the di.'^ease in the sick, is liable to cause in 
jury to liver, kidneys, and other vital organs, whereby the nutrition of 
the animal may be permanently injured. Such medicines, when care- 
lessly given to healthy animals as ])reventives, may irritate the large 
bowel sufficiently to reduce its vitality and power of resistance when the 
disease actually appears. The proper medicine to feed must therefore 
be selected with care, and we trust that experiments to this effect may 
be carried on at the Experiment Station at an early date. 

There is still another line of treatment which demands attention, 
namely, the introduction of a sufficient amount of some disinfectant 
into the body to be absorbed and thus to make the whole body oppose 
the multiplication of bacteria. Koch tried this method by injecting 
mercuric chloride into guinea-pigs and afterwards inoculating them 
with anthrax bacilli. The animals all took the disease and died. 

At the laboratory of the Bureau mercuric iodide, a still more power- 
ful disinfectant, was tried upon rabbits, 

A solution was prepared containing .001 gram mercuric iodide and 
.002 gram potassic iodide in a cubic centimeter. Of this .5 cubic centi- 
meter was injected beneath the skin of the back of four rabbits (Nos. 
1, 2, 3, 4) for eight successive days. On the third day Nos. 1, 2, 3, and 
a fresh rabbit (check\ No. 5, received hypodermically into the inner sur- 
face of the thigh ^ cubic centimeter of liquid containing one millionth 
(Hibic centimeter of a beef infusion culture of hog cholera bacteria about 
one day old. 

All the inoculated rabbits died, the dates being given in the ai)pended 
table. Rabbit No. 4, which had received the iodide only, to observe 
any ])oisonous etteet, remained well. The lesions were those of hog 
cholera, and the specific bacteria were present in the spleen. The total 
amount of the iodide given was .004 gram, about jL grain. 



'So.* 


.5 cubic centimeter of 
f'r, per cent, luercuiic 
iodide daily. 


Inoculated with one-mil- 
lionth cubic centimeter 
culture bog cholera bac- 
teria. 


Ilemiirk.s. 

1 


1 
2 
3 
4 


June 22 to 29, inclusive. 
.... do 


June 2t 

...do 


1 
Died June 30. 
Died July 3. 
Died July G. 

Died July 3. 


...do 

. . do 


...do 


.do 











* Wf'isrliin;; oai'li :ibout 2 pouiid-s. 



138 

At the same time healthy pigs were fed with the same substance in 
minute doses, to observe any toxic effect that might appear. These exper- 
iments were likewise interrupted in tlieir application by the disappear- 
ance of the disease at the beginning of the year. While we therefore 
recommend in general the use of a purgative, such as calomel, in the 
beginning of the disease, and careful feeding subsequently, we have as 
yet no actual experimental evidence that such treatment will be of any 
avail, owing to the frequent interruptions of the work. 



EXPERIMENTS ON THE PREVENTION OF HOG CHOLERA BY 

INOCULATION. 

DiiriiJi;' the piust six or seven years tbe atteutiou of tbe world has 
been centered upon the brilliant experiments of Pasteur in tbe line of 
preventive inoculation for animal diseases. Many others have since 
then followed his footsteps witli variable success. Among those dis- 
eases for wliich preventive inoculation is more or less in vogue in some 
European countries, especially in France, are anthrax among cattle and 
sheep, charhon sympfomatiquc, afiecting the same animals and perhaps 
identical with the disease known as bhick quarter or black leg in this 
country. This is not the place for discussing the absolute value of vac- 
cination in these diseases, nor to point out the reasons why they are 
not regarded of much value by scientists of Germany and other States. 
SufBce it to say that the Bureau has devoted a largo amount of time in 
testing all the available methods of attenuating hog cholera virus for 
vaccinal use, to determine whether any vaccine could be placed at the 
disjiosal of the public that might prevent the enoimous losses entailed 
each year by this dreaded germ disease. In the following pages most 
of the work done (chiefly during the winter and spring of 1880) is briefly 
r('i)roduced 

Inocuhitions of small doses of strong virus in the form of liquid cultures 
was first resorted to, because it had been observed that i)igs rarely take 
the disease when culture liquid in such quantities is injected directly 
under the skin. We reasoned that if injections of suuill doses do not 
cause the disease, why may the}" not prove effective in preventing natu- 
ral infection? The cultures were not therefore attenuated, as Pasteur 
has done, with anthrax, because the step was deemed uunecessarj'. 

A lot of animals were at first inoculated twice with very small quan- 
tities, the period between the two inoculations being about two weeks. 
This time was sufBcient to reveal any disease which might Lave been 
induced by the inoculations. Two weeks after the second inoculation 
the animal was infected either by allowing it to feed upon the internal 
organs of pigs which had died of the disease or by exposing it to the 
sick and dying in an infected pen. It was soon found that the inocu- 
lations were by no means prot ctive, in whatever way the virus entered 



140 

the system, for subsequent feeding usually luoduced cases of the most 
acute character and ^Yith the most severe and extensive lesions. The 
doses of inoculated cultures Avere gradually increased in quantity with- 
out yielding any better results. Of a large number of animals sub- 
jected to inoculation only five took the disease unmistakably as a con- 
sequence of the operation. The experiments, iucluding tables and 
poHt-mortem notes, are given in extenso as they were made. 

In reading them over it will be uoticed that the virus was cultivated 
chietiy in liquid media, and the solid media, more particularly nutritive 
gelatine, were only employed to test the i)urity of the cultures. When- 
ever these cultures were used for inoculations they were previously 
tested on gelatine plates by drawing a i)latinuni wire, dipped into the 
culture, through the gelatine layer two or three times before the gela- 
tine had become solid. Among the hundreds of cultures thus tested in 
the space of several months not one was found impure. Series of cult- 
ures extending uj) to the tenth generation were usually carried on by 
inoculating fresh tubes each day. The last culture tested as describetl 
above gave precisely the same colonies as the first in all the series thus 
far prepared. The culture-tube, described in the First Annual Eeport 
of the Bureau, was used almost exclusively for these cultures in liquid 
media. The advantages and accessibility of cultures in liquids for 
l)urj)oses of inoculation, the readiness and ease with which quantities 
or doses may be determined, finally, certain characteristics of growth 
in liquids, place this nsethod on a level with, if not above, that of solid 
cultures for experimental purposes. For diagnostic purposes, solid 
media are to-day a shw qua non of bacteriological work. 

Experiment 1. — Pigs Xos. 152, 1G7, 1G8, and 175 were inoculated with 
pure cultures in beef-infusion peptone as follows: On January 23, one 
drop of the seventh culture, derived from the spleen of pig No. 114; 
on Februarys, with one eighth cubic centimeter from a culture derived 
Irom a guinea i)ig. Both cultures were ddutcd in sterile normal salt solu- 
tion in such a way that 1 cubic ceutimeter of fluid was injected each time. 
Theinneraspectof the thigh near Pouparl'sligameut was chosen, and the 
iiqnid was introduced beneath the skin into the subcutaneous tissue with 
a hypodermic syringe. There was no perceptible swelling at the site of 
either inoculation, excepting in No. 175, in which there were two tunu^rs, 
each the size of a walnut, at the seat of the first inoculation. In order to 
test the extent of the immunity which these inoculations might have 
conferred, feeding the viscera of pigs which had succumbed to hog 
cholera was resorted to, the animals being transferred to the large in- 
fected ])eu for this puri)ose. Nos. 1G8 and 175 were fed in this way 
March 5, and two animals not inoculated (Nos. 158 and 180) were fed 
with them. All four died; the two vaccinated animals in about twenty 
days, the others in about fifteen days after feeding. March 13, Nos. 152 
and 107 were fed with two check animals, Nos. 176 and 190. These four 
also died of hog cholera; the two vaccinated ones averaging twenty 
days, the others eleven days after feeding. The inoculation may be 
said to have simply retarded death from five to nine days. A table 



141 

giving- a summary of those facts is appemlcd, togetber with a brief 
descriptiou of tha j^ost mortem appearances: 



Ko. 


January 23. 


Fed with hoo;. 
i'"(l)niar.v 8. cholera vi.s 
Cera. 


Died. 


Number of 

d.ay.s after 

feeding. 


152 
1C7 
168 
175 
158 
189 
17(j 
190 


Drops. 

1 

1 
1 

1 


c. c. 

i 

h 
i 


Mar. 13 

Mar. 13 

Mar. 5 

Mar. 5 


Apr. 3 

Apr. 1 

Mar. 28 

Mar. 22 

M.Tr. 91 


21 
19 
23 
17 
10 
H 
10 
12 






Mar. 5 j Mar. 19.... 

Mar. 13 t Mar. 23 

Mar. 13 \ Mar. '>.'>. . . . 



















Auti>2)sy notes. — Xo. 152. Skin of limbs and abdomen dotted with purple 
spots; on abdomen, general reddening. Points of extrava.sation and 
ecchymosed spots throughout the subcutaneous connective and fatty 
tissue and on gastro-splenic omentum. Superticial inguinal glands 
greatly enlarged and congested. Spleen enlarged, filled with l)lood, 
and very soft. Petecchise on epicardiura. Numerous lobules of the lungs 
collapsed. Glomeruli of kidneys ajtpear as deep red petecchi^B. In 
ciecnm and upper portion of colon extensive and deep ulcers, A few in 
the ileum near the valve. The mucosa of the stomach, small and large 
intestine, thickly covered with dark red points or petecchia'. 

JS^o. 1G7. Dying, and hence killed by a blow on the head. Spleen swol- 
len, friable; epicardium dotted with points and spots of extravasation. 
In lungs a few collapsed lobules. Lymphatic glands generally very 
deeply congested, similarly the mucous membrane of fundus of stomach 
and the kidneys. Large ulcers in caecum and upper portion of colon. 

^NTo. 168. Subcutaneous and subperitoneal tissue contains numerous 
ecchymoses from one eighth to three-fourths inch in diameter. Spleen 
enlarged, gorged with blood, friable. Petecchia? on epicardium. Lungs 
not collapsed; its parenchyma contains numerous deepl^^- congested 
areas from one-eighth to one-half inch in diameter. Kidneys enlarged, 
with extravasations on surface and in parenchyma. Cortex of lym- 
phatics in general deeply congested. Extensive, almost continuous, 
ulceration of caecum, and upper portion of colon, in part blackish, the 
remainder of the large intestine being the seat of severe inflammation 
and extravasation. Mucous membrane of stomach similarly involved. 

No. 175. Subcutaneous tissue dotted with pale red spots. Tumor at 
the place of the first inoculation firm throughout, pale yellowish. Su- 
perticial inguinal glands, as well of those of thorax and abdomen, with 
purplish cortex. Spleen tissue still firm, dotted with numerous bright 
red i)oints, but slightly enlarged. Beneath the entire e])icardium and 
endocardium many extravasations. Ctecum and upper portion of colon 
extensively ulcerated. Serous surface of large intestine dotted with 
extravasations. 

No. 176, Slight reddening of skin and subcutaneous fatty tissue. 
Cortex of lymphatic glands in general deeply congested. Spleen much 
eidargcd and surface dotted with numerous bright red elevated jioints. 
A lew ])etccchi;Te on endocardium and epicardium. Lungs deeply con- 
gested throughout; kidneys likewise inflamed. Stomach slightly red- 
dened at fundus; small intestine also slightly congested. Serosa of large 



142 



intestine dotted with extriiviisatious. Tlie mucosa of caecum and small 
portion of colon one mass of necrosed tissue. Walls thickened. 

^o, ISO. Exlensi\'e and dee}) reddeninj;' of skin of abdomen, throat, 
and limbs. Subcutaneous tissue oidy slightly reddened; spleen en- 
hiiiicd, gorged with blood, friable. Besides the general congestion of 
the lungs there are small darker areas, representing hemorrhagiclobuies. 
IJronchial glands and those along lesser curvature of stomach swollen 
and gorged with blood; the other lymphatics only moderately congested. 
Besides a small number of ulcers throughout the large intestine, the 
mucous membrane is deeply congested and dotted with occasional 
hemorrh;igic i)oints. Kidneys extensively inflamed ; on section the cor- 
tex shows extravasations. 

No. 190. Considerable reddening of the skin of abdomen and ventral 
aspect of limbs; very slight in subcutaneous tissue. Spleen greatly 
enlarged, dark ])urple; blood flows freely on cutting into it; very soft. 
Lungs contain regions of congestion and hepatizations, possibly due 
to the presence of a few lung worms. Lymphatic glands near stomach, 
tlie bronchial and superficial inguinal glands, deeply congested. Mu- 
cous membrane of stomach extensively congested; a large patch of 
extravasaiion in fundus; large intestine severely inflamed, with occa- 
sional extravtisalions; no ulcerations. 

The diagnosis of hog cholera was confirmed in every case by finding 
the specific bacillus in cover-glass preparations of splenic tissue and 
obtaining therefrom juire cultures in liquid media and in gelatine. 

Experiment 2. — In conjunction with the first series of inoculations, two 
pigs (iS^os. 149 and ICl) were inoculated at the same time, as follows; 
January 23, with 1 cubic centimeter of the seventh culture in beef-infu- 
sion i)eptone. No reaction at the place of inoculation in No. 149; a 
tumor as large as a marble in No. 161. On February 8 both received a 
second injection of 1 cubic centimeter. Two swellings as large as a 
chestnut at the place of the second inoculation in No. 149; in No. IGl 
also a considerable thickening was present. No. 149 was fed March 
5 with four of the jueceding series; No. 101 on March 13 with the 
remainder of the preceding series and some to be subsequently spoken 
of. Both died of hog cholera. The accompanying table and brief 
autopsy notes explain themselves : 



No. 


Inoculation. 


Fed. 


Died. 


Daya 

after 

feeding. 


Jau. 23. 


Feb. 3. 


149 
ICl 


c. c. 

1 
1 


c c. 
1 

1 


Mar. 5 
Mar. 13 


Mar. 24 
Apr. 14 


19 
32 



No. 149. Slight reddening of the skin and subcutaneous connective 
tissue; the tumors produced by inoculation firm, pale yellowish, only 
one showing soitening within ; spleen considerably enlarged and full of 
blood; ascarides in gall bladder, which is ulcerated; mucous membrane 
along fundus of stomach intensely congested; the mucous membrane 
of ctecum and upper portion of colon one mass of ulcers; in the remain- 
der of colon they are isolated; kidneys con^rested. 



143 

No. IGl. Great ciiiaciatioii; si)leen eiilarj^eil aii<l gorged with blood, 
very soft; all ex('ei)tiiio- the i)osterior re<;ion of each ]i'n«;- hei)atize(l 
and the bronchi tilled with a tliiek ereaujy mass, whieh consists almost 
entirely of pus corpuscles ; Iynii)hatics but slightly con.uv'sted ; adhesions 
between adjacent coil of larj^e intestine and bladder; c;ecum and colon 
studded with larj^e deep ulcers; valve greatly enlarged ; intense con- 
gestion of mucous membrane of fundus of stomach. 

Cover glass pre])arations from the spleen of both contain the charac- 
teristic bacilli. Gelatine and liquid cultures irom the same organ were 
I)ure. 

The comjiaratively large dose of strong virus used for vaccination was 
not capable of protecting these animals from the disease communicated 
by feeding. There was no suspicion of disease caused by the vaccination 
when they were fed, and the time intervening between the two injec- 
tions was sufficient for any development of disease from the injected 
virus. 

Experiment 3. — Pigs Nos. 151, 169, 170, and ITS were inoculated as 
in the i)roceding experiments on February 8 and 23 with ^ cubic centi- 
meter of a beef infusion pci)tone culture derived from a guinea pig and 
the seventh culture from the spleen of a pig in the same medium. The 
dose was diluted in salt solution so as to make 1 cubic centimeter of 
liquid. In No. 151 the second inoculation produced a tumor about 1 
inch long and one third inch thick. The 15rst was scarcely noticeable. 
In No. 109 the first inoculation resulted in a bcairlike nodule; the sec- 
ond produced several of tbe same siz(\ In No. 170 neither inoculation 
showed more tlmn a veiy slight swelling. In No. 178 both inoculations 
produced rather extensive swellings. 

On being fed with the viscera of pigs known to liave died of the dis- 
ease all took the disease and died ; two on March 13 and the remain- 
ing two on March 19, i. e., one in thirteen, one in eighteen, and two in 
twenty-two days after feeding. A table summarizing these facts and 
brief j)o.s/-?«or/eHi notes are appended: 



No. 


InoeiilatioD. 


Fed 


Died 


Days 

alt'i T 

feeding. 


Feb. 8. 


Feb. 23. 
c. c. 




Mar. 2(5 


151 


c. c. 
h 


Mill-. U 


13 


1G9 


i 


i 


Mar. 19 


A'lr. 10 


oo 


170 


k 


h 


Mar. 13 


A in: 4 


22 


178 


i 


i. 


Mar. 19 


A-pr. C 


18 



Autopsy notes. — No. 151. Purplish spots on skin of abdomen and paler 
ones in subcutaneous tissue. Inoculation tumor cuts like cheese; yel- 
lowish-white. Extravasations under endocardium and pericardium; 
left lung mottled from hemorrhagic areas ; cortex of lymphatic glands 
intiltrated with blood ; those of meso colon and lesser curvature of 
stomach dark purple throughout ; kidneys pale; hemorrhage into pel- 
vis of left kidney ; extravasations into mucosa of stomach; moderate 



144 

number of ulcers in CiTecuin aud colon ; large quantity of blood in the 
lower C or 8 feet of ileum aud in the large iutestiue, clotted in tlie 
former tube, wliere the mucous membrane is deeply congested. 

No. 169. Small tuuior on the left side, the place of the second inocu- 
lation ; spleen enlarged aud congested, with large hemorrhagic infarcts; 
considerable effusion in the large serous cavities. Besides the general 
congestion of lungs, there are scattered throughout its parenchyma 
hemorrhagic foci. Hemorrhagic intiammation of kidneys manifested 
by bright red glomeruli throughout its cortex; lymphatics in general 
dee))ly reddened; numerous petecchia3 in stomach, small and large intes- 
tine. In coecum and colon, large, deep ulcers. 

No. 170. Redness of skin in abdomen ; nothing at places of inoculation ; 
spleen enlarged, friable, full of blood ; abdomen, thorax, and pericardial 
cavity contain much yellow serum; congestion of the lungs with darker 
hemorrhagic foci throughout; anterior lobes collapsed; kidneys enlarged, 
with a few extravasations on surface and in parenchyma ; mucous mem- 
brane of stomach and intestines covered with many hemorrhagic points 
and spots. In large intestine, including rectum, numerous old ulcers, 
some 1 inch across. Lymphatics in general hemorrhagic. 

No. 178. Died quite unexi^ectedly. At the place of first inocula- 
tion two firm whitish masses; spleen enlarged, friable ; its substance 
contains hemorrhagic infarcts; extravasations beneath both serous sur- 
faces of the heart; congestion of lungs, with numerous darker hemor- 
rhagic foci; lymphatic glands of abdominal cavity very dark and gorged 
with blood; extensive ulceration about the ileocajcal valve, in the cje 
cum, and colon; in the lower portion of colon and in the rectum numer- 
ous small extravasations. Hemorrhage into pelvis of both kidneys. 

The post-mortem determination of a severe type of hog cholera in 
these four cases was confirmed by finding in the spleen of each animal, 
by means of cover-glass preparations, numerous specific bacteria of this 
disease. Cultures in liquid media made from every spleen were found 
pure when examined microscopically as well as on gelatine plates. This 
experimc nt likewise proved the inefficiency of small quantities of non- 
attenuated virus introduced beneath the skin in j)reventingan invasion 
of the micro organism from the alimentary canal. 

Experiment 4. — A third lot of four pigs (Nos. 117, 171, 172, and 171), 
between three and five months old, were inoculated as before with .2 
cubic centimeter each from the second beef infusion peptone culture 
derived from a pig's s[)leen. On March 1 they were inoculated with 
.2 cubic centimeter from the second culture derived from a pig's spleen. 
In No. 117 there was a slight swelling after the first, aud one as large 
as a chestnut after the second inoculation. In No. 171 a mass 1^ to 2 
inches long and three-fourths inch in diameter was found at site of the 
first iuoculation. There was but a small nodule at the place of the 
second inoculation. In No. 172 two lumps, like small marbles, formed 
after the first inoculation ; after the second only a small nodule formed. 
In No. 171 the reaction after the second inoculation was manifested by 
an irregular tumor about 2 inches long and one third of an inch in diam- 
eter, the reaction at the place of the first inoculation being less marked. 

Of those four, two (Nos. 117 and 172) were fed with the \iscera of 
pigs dead from hog cholera, together with two control animals (Nos. 



145 



193 and 193), oil March 19. The rest (Nos. 171 and 174) were simply 
jVIaced in the large infected pen March 22, with those that had been fed 
with infectious matter. Below the result is given in a tabulated form. 
It shows that all the animals succumbed to the disease, those simply 
exposed by contact with the sick as well as those fed. Of the inocu- 
lated animals, those fed died in twenty-one and eighteen days after 
feeding; those exposed, in twenty two and twenty-five days, respect- 
ively. Those not inoculated died twelve and nine days, respectively, 
after feeding. Here, likewise, we notice the prolongation of life in the 
inoculated pigs. 



No. 

117 
17t 
172 
174 

loa" 

193* 


Feb. 13. 


Mar. 1. 


Date of feeding 
and exposure. 


Died. 


Days after 

exposure 

and feeding. 


c. c. 

. 2 

.2 
. 2 
. 2 


c. c. 
.2 

.2 
.2 
_ 2 


Fed Mar. 19 

Exposed Mar. 22.. 

Fed Mar. 19 

Exposed Mar. 22.. 

Fed Mar. 19 

do 


Apr. 9 
Apr. 13 
Apr. 6 
Apr. 16 
Mar. 31 
Mar. 28 


21 
22 
18 
25 
12 
9 













* Checks. 

The lesions found at the autopsies of these pigs are briefly as follows: 

]S"o. 117. Extensive reddening of the skin of abdomen ; gTeat enlarge- 
ment of spleen, which is gorged with blood, very soft; petecchial dis- 
colorations on surface of lungs and on section ; large intestine studded 
with broad, deep ulcers as far as tbe rectum; a few in fleum. 

No. 171. Skin over ventral aspect of body deeply reddened ; hemor- 
rhagic spots under peritoneal covering of diaphragm and large intestine 
and under capsule of kidneys; lungs congested, containing numerous 
dark hemorrhagic lobules ; part of anterior lobes collapsed. The spleen 
very large, dark colored; nodes slightly raised above surface, shown on 
section to be hemorrhagic infarcts; lymphatic glands generally highly 
congested ; petecchial spots on surface and in cortex of kidneys; hemor- 
rhagic foci throughout mucosa of stomach and intestines. About four 
large ulcers in ciecnm and colon. 

No. 172. Reddening of skin of ventral aspect of body and of subcu- 
taneous tissue generally; firm, pale yellow, cheesy masses, surrounded 
by a thin membrane at place of inoculation ; engorgement of spleen 
and lymphatic glands; extravasations in parenchyma of kidneys. In 
caecum and colon numerous deep ulcers, some coalesced. Mucosa of 
stomach generally congested, and that of intestines thickly dotted with 
petecchia?. 

No. 174. Deep reddening of skin of abdomen; encysted cheesy mass 
at site of first inoculation ; great enlargement of spleen ; prominent red 
points on surface ; effusion into abdominal cavity ; anterior lobes of 
lungs collapsed, remainder normal; lymphatics highly congested ; three 
large ulcers in CiEcum ; valve thickened and ulcerated ; petecchiic numer- 
ous throughout mucosa of stomach and intestines. 

No. 192. Control animal ; reddening of skin of ventral aspect of body 
and of subcutaneous tissue; spleen swollen j full of blood ; friable; at- 
15512 H c ^-10 



146 

electasis of tlie small anterior lobe of each lung ; ulcers on the mucous 
surface of gall bladder ; cortex of lymphatic glands infiltrated with 
blood ; mucosa of large intestines congested; numerous ulcers in caecum 
and upper colon. 

'^o. 193. Subcutaneous connective tissue considerably reddened ; 
spleen but slightly enlarged ; not much softened ; mucous membrane 
of stomach, of large and small intestines, deeply congested ; contents 
of large intestine fluid, chocolate color.ed. 

In cover-glass preparations from the spleen pulp of these animals, 
numerous bacteria of hog cholera were found in each preparation. Both 
gelatine and liquid cultures from every spleen proved to be pare cult- 
ures of the bacillus of hog cholera. 

The diagnosis made on post mortem was thus confirmed by micro- 
scopic examination and culture. 

Experiment 5. — To determine the effect of a single inoculation, on 
February 13 two pigs (Nos. 115 and 160) received subcutaneously each 
1 cubic centimeter of the second beef infusion peptone culture obtained 
from the spleen of a \>\g. In IsTo. 115 a tumor as large as a marble was 
found at the seat of inoculation March 9. In No. 160 the tumor was 
elongated, about 2 inches long and three-eighths of an inch thick. No. 
115 was fed with viscera taken from cases of hog cholera March 19. 
No. 160 was simply exposed to the disease by being transferred to the 
large infected j^en. No. 115 died April 8. No. 160 recovered and was 
well May 6. The detailed account of this experiment is appended : 



• 


Tel). 13. 


Date of feeding and 
exposure. 


Effect. 


Days after 
feeding. 


115 

IGO 


c. c. 
1 

1 


Fed Mar. 19 

Exposed Mar. 22 


Died Apr. 8 . 
Kecovered . . 


29 



Post-mortem yiotes. — No. 115. Firm, i^ale yellow tumor at seat of in- 
oculation, encysted ; center undergoing softening. Spleen tumefied, 
very dark and friable. A few extravasations beneath serous coverings 
of heart. In cortex of kidneys numerous hemorrhagic points ; cystic 
degeneration of right kidney; advanced ulceration of ciecum and 
colon ; scattered petecchicie in mucosa of stomach and small intestine. 

No. 160. Was very low for a time, beginning with April 1. It was 
barely able to stand and its appetite was poor. It rapidly recovered, 
however, and was gaining flesh in May. Whether the animal was suffer- 
ing from hog cholera or from the l^clerostoma pinguicola (kidney worm), 
with which some of this lot were found affected, can not be said. 

In order to determine whether a single injection of a comjiaratively 
large quantity of culture liquid, while not inducing the disease, would 
protect against the disease itself, the following experiment was per- 
formed : 

Experiment 6. — Four pigs (Nos. 202, 204, 205, and 212) were inoculated 
April 2 with 1 J cubic centimeters of a seventh culture in beef infusion with 
1 percent, peptone one day old. Four additional pigs (Nos. 206, 207, 208, 



147 

and 209) received but one cubic centimeter of the same culture. The re- 
maining four of the same lot (Nos. 203,210,211, and 213) were reserved as 
checks upon the experiment. Of these ISTos. 203 and 213 had a temperature 
of 106"^ F., and hence were suspected of disease. This suspicion was soon 
confirmed after they had been placed in a pen alone. Both had a severe 
diarrhea, one dying April 11, the other Ai^ril 13. The lesions were con- 
fined to the mucous membrane of the large intestine, which was dotted 
with numerous elevated lemon yellow tough masses a few lines across, sim- 
ulating ulcers. On close examination, however, this impression was dis- 
X)elled. These tough masses were easily removed hi toto from the mu- 
cosa, which ij)resented a slight depression without any loss of substance. 
They were evidently exudates from the mucosa (croupous ?). There were 
no bacteria in the blood or in a bit of spleen dropped into a culture tube. 
No development took place in either tube. 

Of those inoculated with 1^ cubic centimeters two died from the imme- 
diate effects of inoculation. No. 204 died in eleven days and No. 212 in 
seven days. In No.204 atough tumor had formed atthe point of inocula- 
tion on each side. The mucous membrane of the large intestine was com- 
pletely necrosed and the spleen enlarged. In No. 212 local swelling was 
present on one side. The stomach and large intestine were deeply con- 
gested, with points of commencing ulceration in the latter. In both ani- 
mals the bacillus of hog cholera was presentin cover-glass preparations of 
the spleen. Nos. 202 and 205 seemed to remain unaffected by the inoc- 
ulation. One month and a half later both were exposed to the disease 
in the large infected pen. A mouth later they were removed with oth- 
ers to a clean pen, after having apparently resisted infection. No. 202 
was gradually wasting away, and died July 24, more than two months 
after exposure. In the large intestine were cicatrices of healed ulcers 
and such as were healing. The severest lesions were in the lungs. Both 
were adherent by means of bands to the costal pleura, and were exten- 
sively hepatized. No. 205 was alive and well August 15. 

Of the second lot, which had received 1 cubic centimeter of the same 
culture the results were nearly the same. Two succumbed to the inocula- 
tion, one died of infection, and a fourth survived. No. 208 died fifteen 
days after inoculation. Besides the inoculation swellings, enlarged and 
congested spleen, the mucous membrane of the largeintestine was covered 
with extensive deep ulcers, and the walls much thickened and softened. 
The corresponding lymphatics in the meso colon deep purple. No. 209 
died in six days after inoculation. There was general congestion and 
extravasation of blood in the internal organs, involving the entire mu- 
cous membrane of the alimentary tract, especially the large intestine, 
the lymphatics and serous membranes, the spleen, and kidneys. Ulcera- 
tion had not yet begun. In both animals the spleen was crowded with 
bacteria and furnished pure cultures of the specific germ. 

Nos. 20G and 207 were not affected by the inoculation. They were 
exposed with the iirecedinglot, as indicated in the table. No. 207, after 



148 



appareutl^" resisting iufection in the infected pen for a month, diedJuly 
18, after liaving been in a clean pen since June 21. The extensive ne- 
crosis of the mucous membrane of the caecum and upper portion of colon, 
with the absence of any acute inflammation elsewhere, gave evidence of 
a chronic case of hog cholera. No. 20G, though still alive, is emaciated. 

The two remaining check pigs, which were exposed with the preced- 
ing animals in the same infected pen, both died of hog cholera; No. 
211 found dead June 21. The most marked changes were a small num- 
ber of ulcers on a pale mucous membrane scattered over the caecum and 
colon. No. 210 lived a month longer than its mate. The existence of 
hog cholera was demonstrated by a general necrosis of the mucous 
membrane of the CiBCuiu and an extensive pigmentation in the remain- 
der of the large in testine. The lungs were adherent in places and much 
congested. 

When we gather together the facts presented by this experiment we 
shall find a certain number of interesting c" ductions springing there- 
from. In the first place, we note the peculiarity of the intestinal lesions 
of the two animals which died from some unknown cause, presumably 
not hog cholera. We next point to an additional demonstration of the 
specific nature of the bacillus of hog cholera, for out of eight inoculated 
four died, and the age of the lesions corresponded well with the length 
of time elapsing between inoculation and death. 

Those animals which resisted the inoculation were in part protected, 
as two among four were still alive on August 17, and the remaining two 
died, probably from effects of the ulceration, months after exposure. 



No. 


Inoculattd April 2. 


Died from 
inocu- 
l;it ion. 


Exposure 

in 

infected 

peus. 


Kemoved 

from 
infected 

pens. 


Remarks. 


*202 
204 


1^ c. c. culture liquid. 
do 


April 13 


May 18 


June 21 


Died July 4. 


203 


do 


....do .. 


June 21 


Alive August 17. 


0]^9 


do 


April 9 




206 


1 c. c. culturo liquid .. 


May 18 


June 21 


Alive Augu-st 11, but unthrifty. 
Died July 18. 


207 


.. do 




203 


do 


April 17 
April 8 






209 


do 








t203 








Died April 11, irom a )nie unknown dis- 
ease. 

Died Julv 21, of hog cholera. 


1210 






May 18 
...do .. 


Juno 21 


1211 


j 


Died Juue 21, of hog cliolera. 


1213 








DiiHl April 13, from sarao disease as No. 
20.3. 











* These animals were one and a half months old at date of inoculation. 1 Checks. 

Experiment 7. — Having determined that even large doses of liquid 
cultures of the bacillus of hog cholera can be borne without produc- 
ing the disease in most cases, it was thought advisable to make two in- 
oculations of strong virus, a first one with a small quantity and a second 
with a large quantity. 



149 

First inoculation, April 21 : Xos. 214, 227, 223, and 222 received ^ 
cubic centimeter of a tbiid culture in beef inlusiou coutainiug 1 per 
cent, each of peptone and glucose. Tbe liquid was diluted with sterile 
salt solution, so as to make i cubic centimeter. It was injected, one- 
half beneath the skin of each thigh. After waiting two weeks, in order 
to determine whether the inoculation had not produced disease, a second 
injection was practiced May G, the thirteenth and fourteenth cultures 
of the same series being used for this purpose. The animals received 
1, li, 2, and 2^ cubic centimeters of the culture li(piid, respectively. 
No untoward results following the injection of these large doses, they 
were transferred to the large infected pen May 25. 

A second lot (yos.22G, 228,215, and 229) were treated in precisely the 
same way and at the same time, excepting in receiving i cubic centi- 
meter for the first dose instead of 4- cubic centimeter. 



No. 


First 

inoculation, 

Apr. 21. 


Second 

inoculation, 

May U. 


Expos- 

uie in 

infected 

pen. 


Time of 
death. 


Days 
after first 
exposure. 


214 
227 
223 
232 
226 
228 
215 
229 
*224 
*225 


c.c. 

i 

i 
i 
i 
i 
J 
i 
4 


c. c. 
1 

2 

2i 
1 

n 
2 

2h 


May 25 
...do .... 
...do .... 
...do .... 
...do .... 
...do .... 
...do.... 
...do ... 
...do .... 


July 1 
June 27 
July 2 
July 1 
July 3 
July 13 
July 30 
June 27 
Aug. 4 
June 27 


37 
33 
38 
37 
39 
49 
46 
33 
71 
33 






do 









' Checks. 



No. 214, being in a dying condition July 1, was killed. In the cfEcum 
and colon were found very large, deep, blackish ulcers upon a pale mu- 
cosa. The case was evidently one of chronic hog cholera. A pure 
liquid culture of the hog cholera bacillus was obtained from the spleen. 

No. 2'J,7 died June 27. The lymphatic glands were deeply congested ; 
the mucosa of large intestine was generally pigmented and co\ere<l 
with large blackish ulcers. Small yellowish ulcers were also found in the 
ileum. The i^oints of injection were occupied by encysted, partly lique- 
fied masses. 

No. 223 was found dead July 2. At the i)oints of injection encysted 
masses were found, the contentsof one of which were discharging through 
an opening in the skin. The mucosa of the entire large intestine deeply 
congested. Scattered ulcers of varying age and size in the caecum and 
colon. Bacilli in spleen. 

No. 232, after a period of unthriftiness, was found dead July 1. The 
autopsy revealed a chronic broncho-pneumonia, with pleuritic adhesions 
of right lung. The mucous membrane of the cnecuiu and colon, besides 
being studded with a large number of shallow ulcers, was deeply and 
uniformly congested, the congestion involving also the lower portion of 
the ileum. On both thighs an encysted semi-liquid mass indicated the 
seat of the inoculation. 



150 

Of the second lot, which had received ^ cubic centimeter of the first 
inoculatioD, all succumbed to the infection. 

Ko. 226 died July 3. The characteristic lesion was extensive ulcera- 
tion, together with deep congestion of the mucosa of large intestine. 
Encysted masses at the points of inoculation. A considerable number 
of hog cholera bacilli in the spleen. 

No. 228 died July 13. In this animal the mucosa of c.Tcum and colon 
presented a continuous mass of necrosed blackish tissue, the ileo-ccccal 
valve being enlarged to twice the normal size. A few scattered yellow- 
ish ulcers in the lower portion of the colon. 

No. 215 died July 10, probably affected in the same way, though no 
postmoricm examination was made. 

iSTo. 229 died July 27. In this case the lymphatic glands were in 
general deeply congested; ecchymosis beneath the serous membranes. 
Pigmentation of the mucous membraneof the stomach, duodenum, ileum, 
and large intestine from former extravasations. Several large ulcers 
on the valve and some others in colon. Ulcers in the cardiac portion 
of the stomach. Encysted masses at the jmint of inoculation. 

Nos. 221 and 225 were penyed with the above eight animals as checks. 
No. 225, after being sick for a few days, was found dead June 27. The 
mucosa of the caicum and upper half of the colon was extensively pig- 
mented and ulcerated, the lower half deeply congested. The ileum ul- 
cerated for 5 or feet from the valve. Many of the ulcers were so deep 
astohave produced inHammation of the serous membrane and thickening 
of the intestinal walls. The other check (No. 224) lived over two months 
after exposure, being unthrifty during this period. On post-mortem ex- 
amination the mucosa of large intestine was considerably pigmented, 
and scars of healed ulcers were present. A large suppurating wound 
of the lower jaw, involving the bone, may have contributed towards 
the fatal issue. 

Experiment 8. — These inoculations having failed to produce immunity 
from natural infection, another experiment was tried by augmenting 
the dose of strong virus used for the second inoculation. Thus Nos. 
239, 242, 244, and 215 received each | cubic centimeter for the first in- 
oculation May 27, No. 243 being retained in the same pen as a check. 
Of these No. 239 died of hog cholera as the result of the inoculation. 
The remaining three, received two weeks later, on June 10, 2 cubic cen- 
timeters each of strong virus. The cultures were prepared in beef in- 
fusion with 1 per cent, peptone. They were usually the third or fourth 
culture, not more than one day old. A second lot (Nos. 240, 254, 255, 
and 256) were inoculated at the same time and in the same way, with 
this exception, that the second dose was increased to 3 cubic centime- 
ters. On June 24 all were placed in the large infected pen. 

No. 239 died June 2, within six days after receiving i cubic centime- 
ter of the culture, and as a result of the inoculation. The lesions were 
those of a very acute case, engorged spleen and lymphatics, intense con- 
gestion of the mucosa of the large intestine and of the intestinal tract 
in general. The lungs w'ere likewise engorged and dotted with extrava- 
sations. This animal was eating and apparently well on the morning 
of death. The spleen was crowded with bacilli of hog cholera, and pure 
cultures were obtained from it. 

No. 242 died July 17. The characteristic lesions of hog cholera were 
found in it; extensive ulceration of the ceecum and colon; engorgement 



151 

of spleeii and lymphatic glands with blood. Encysted masses at the 
lioint of inoculation. No. 224 succumbed July 9 with practically the 
same lesions, besides the presence of a considerable quantity of serum 
iu the abdominal cavity. 

The check to this lot died July 13. The depth of the ulcerations in 
the cfficum and colon had implicated the serous covering, so that adhe- 
sions had formed between the caecum antl abdominal walls. Punctiform 
ecchymosis on serosa of ileum ; the mucosa not affected. The mucosa 
of ctecum was found completely ulcerated, the necrosis stopping ab- 
ruptly at the edge of the valve; iu the colon the necrosis resolved itself 
into large isolated ulcers. 

Of the second lot, No. 240 died July 10. At the place of inoculation 
a firm pale yellowish mass, about 1 inch long, was found. The lower 
portion of ileum, the caecum, the upper portion of colon, contained ul- 
cers of different sizes. The duodenum was occluded by a clot of blood. 
No. 254 died the same day, with lesions of a similar character. No. 255 
died July 20. The spleen in this case was greatly augmented in size 
and gorged with blood. The right lung was congested and adherent to 
wall of thorax ; considerable effusion iu this pleural sac. The cjecum 
and upper i)ortion of colon covered with deep blackish ulcers. A few 
small ulcers in ileum. 



No. 


lirst 
inoculation 

May 27. 


Second 

inoculation 

June 10. 


Expos- 
ure in 
infected 
pen. 


Time 
of death. 


Days 
after tirst 
exposure. 


239 
242 
244 
245 

*243 
240 
254 
255 
256 

*253 


c.c. 

i 
i 
i 


c.c. 




June 2\ 
July 17 
July 9 




2 
2 
2 


June 24 
...do .... 
.. do 


23 
15 


...do ... 


July 13 
July 10 
...do.... 
July 20 


19 
16 
16 
26 


h 
i 


3 
3 
3 
3 


...do.... 

..do .... 

...do .... 

do 



















' Chect. 



t From inoculation. 



The foregoing experiments demonstrate the important fact that pigs 
can not be made insusceptible to hog cholera by subcutaneous injec- 
tions of pure cultures of hog cholera bacteria, according to the method 
used by Pateur in anthrax vaccination. They show how injudicious it 
is to draw conclusions extending to infectious diseases in general from 
experiments made upon one disease only. 

THE EFFECT OF FEEDING SMALL QUANTITIES OF CULTURES. 

It has been already demonstrated (p. 107) that hog cholera can be pro- 
duced in pigs by feeding such as had been starved for a day with con- 
siderable quantities of cultures of the specific bacteria. From 200 to 
400 cubic centimeters of a beef-infusion culture were necessary to de- 
stroy the animal. 



152 

Assuming that small doses may produce a mild form of the disease, 
it seemed worth while to determine whether animals which had beeu 
fed with small quautities of culture material would resist infection when 
placed with sick auimals in thoroughly infected pens. The following 
experiment shows that even after this treatment pigs are still suscepti- 
ble to the disease : 

Nos. 379, 380, 381, 382, and 370 were starved for thirty-six hours and 
then fed pure cultures of hog cholera bacteria in simple beef infusion. 
The quantities given are tabulated below. They were diluted with 
")eef broth to facilitate feeding. 



No. 


Age, Jan- 
uary 21. 


Quantity 
of culture 
liquid fed. 


Placed in 

infected 

pen. 


Died in 

infected 

pen. 


No. 
of days 
after ex- 
posure. 


380 

379 

382 

381 

370 

t383 

t387 

t394 

t399 


5 months . 

...do 

....do 

...do 

...do .... 

4 months . 


c. c. 
10 

20 

40 

CO 

100 


Apr. 15 
...do .... 
...do .... 
...do .... 
...do ... 

Apr. 19 
do 


June 20 
May 24 
May 10 
May 31 
Apr. 20* 
May 11 
Apr. 30 
May 17 


66 
39 
25 
46 
5 
22 
11 
17 




...do 




Apr. 30 
..do 


....do 















*From injury. 



t ChecliS. 



All appeared to be affected by the feeding on the following day by 
refusing food more or less. Slight improvement on the second day, with 
the exception of 381. On the third day 381 still very ill. On the fourth 
day 382 seems more affected than 381. Within the next few days 382 
refuses food, the rest eat. In the second week they had recovered. 
The growth of 382 was materially checked by the feeding, so that it 
had not gained any weight even after several months. 

April 15 they were transferred to a pen infected with hog cholera, in 
which acute cases had lately appeared. A number of check animals 
were transferred to the same pen soon after. The result may be briefly 
summed up as follows: 

No. 379 began to fail from May 10 and died May 24. Lymphatic 
glands generally enlarged and congested; those of mesocolon very 
much so. Spleen very much enlarged; quite firm. Large number of 
yellowish coagula in abdominal cavity. Adhesions between ciecum 
and adjacent organs. Liver very mucli cirrhosed ; gives a gritty sen- 
sation when cut. Several deep, extensive ulcers from 1 to 2 inches 
across in caicum, involving the serous membrane. In lower colon and 
rectum considerable congestion and hemorrhage. Lungs normal, with 
exception of a few subpleural ecchymoses. Both sides of heart filled 
with white thrombi. This animal, therefore, had chronic hog cholera, 
which, no doubt, caused the fatal peritonitis. 

No. 382, the stunted pig, showed signs of the disease May 1 and died 
May 10. Very emaciated ; connective tissue of body stained deep yel- 
low. Spleen very large and full of blood. Lymphatics but slightly 
enlarged and reddened. Considerable yellow serum in abdominal 



153 

cavity. Right lieart filled with dark and washed clot. Lungs normal, 
excepting- a few subpleural ecchymoses. Extreme cirrhosis of liver. 
Mucosa of great curvature of stomach deeply congested, mucosa of large 
large intestine in patclies. 

No. 381 took sick soon after its removal to the infected pen, bnt the 
disease seemed to be mild until it was found dead INIay 31. Animal 
with a fair quantity of fat. Skin of ears, pubis, and throat deeply red- 
dened. Lyu^phatic glands geueraliy enlarged and infiltrated with blood. 
Spleen very mucli enlarged, but tissue quite firm. Lungs hypostatic; 
no liepatization. Epicardiuni covered with pale spots of extravasation. 
Liver i)artially sclerosed; hepatic ducts tilled with viscid yellow bile. 
Medulla of kidneys dotted with petecchia^. Mucosa of large intestine 
apparently normal. In tbe lower colon the feces are blood-stained, and 
occasional small clots are loosely attached to mucosa. 

No. 370 was injured by fighting after being transferred to the infected 
pen so as to be scarcely able to stand, and died April 20. On both 
hind limbs there was extensive extravasation in the subcutis. Tbe super- 
ficial iuguinal glands were deeply congested. Spleen enlarged and 
30ugested. A moderate number of bacteria present, which are not hog 
cholera bacteria as shown in cultures. Left lung collapsed, reddened 
in part and adherent to chest* wall by a plastic exudate. Centers of 
acini of liver deep red, tissue soft. Kidneys congested. Stomach con- 
gested along fundus ; digestive tract otherwise normal. This animal 
died from injury to limbs and lung, and there may have been septic 
infection as indicated by bacteria in the spleen. 

No. 380 became ill May G, died June 20. Decomposition advanced. 
Lungs and glands normal. Liver small, sclerosed. Superficial necrosis 
in cjccum and upper colon with cicatrices of healing ulcers. 

Gelatine tube cultures from the spleens of 382, 383, and 397 showed 
innumerable colonies of hog cholera bacteria. Cultures from the spleen 
of 381 remained sterile. A larger number of cultures would probably 
have shown their i)resence. 

As to the fate of the check pigs exposed with the preceding lot very 
little need be said. 

No. 383 had been fed with 250 cubic centimeters of a beef-infusion 
culture of the hog cholera bacteria from Nebraska as far back as De- 
cember 19. It recovered, however, after an illness of three or four days. 
March IG it received a tracheal injection of swine plague bacteria, with- 
out any untoward result. It was exposed to hog cholera as a check 
April 19, and died very suddenly May 11. It had hemorrhage in sub- 
cutis, lungs, lymphatic glands, in stomach, small and large intestine. 
In the Ciccum there was an ulcerated patch about 2 inches across. Its 
base was very firm and nearly one third inch thick. Was the ulcer the 
result of the feeding five months ago? 

No. 387 became very dull and oil' feed one week after its removal to 
the infected pen, and died A])ril 30. Skin of abdomen reddened. Lym- 
phatics generally hemorrhagic. Ecchymoses on lungs. Extravasations 
in medulla of kidneys. Beginning ulceration in large intestine. Con- 
gestion and slight hemorrhage in fundus of stomach. 

No. 394 died May 17 after a few days of dullness. Hemorrhagic con- 
dition of spleen and lymphatic glands. Inflammation and extravasa- 
tion in stomach. Ulceration and intense congestion of large intestine. 
Ecchymoses beneath pleura of lungs. 

No. 399 was alive and apparently well June 15. Hog cholera bacteria 
were found in the spleen of 387 and 394, especially numerous in the 
latter. They were not looked for in 383. 



154 

There was no protection from the feeding of cultures even in those 
animals which were most severely affected thereby. There was, how- 
ever, a marked ditference between this lot and the check animals, in 
that the latter died of the most severe septicemic or hemorrhagic type 
of the disease, while the former succumbed to a chronic infection. If 
we take the average duration of the disease in the pigs fed with cult- 
ures and those not fed, the ratio will be approximately as 19 to 8 or as 
2^ to 1. These figures indicate a considerable retardation of the fatal 
issue, which is equivalent to a partial immunity. Another fact of im- 
portance needs to be considered in connection with these figures. Three 
Of the pigs fed with cultures were affected with a more or less advanced 
cirrhosis of the liver and the post-mortem notes will show that this liver 
disease largely contributed to the death of the animals. An important 
question arises in this connection as to the origin of the cirrhosis. It 
may have been due to the feeding of the cultures. If so, the remedy 
would be as bad as the disease. But even setting aside this possibility, 
the method of feeding living bacteria ^an only have a theoretical im- 
portance in leading to other methods. It not only scatters the living 
virus, but it may Induce ulceration in the large intestine which, while 
not recognizable, maybe slowly destroying the animal. 

INJECTIONS OF STERILIZED CULTURE LIQUID TO PRODUCE IMMUNITY. 

Bacteriological investigations of the past few years have shown pretty 
conclusively that during the multiplication of pathogenic bacteria there 
are formed chemical substances or j)tomaines which are poisonous to the 
animal economy. The researches of Brieger have done more than any 
others to confirm this theory. It is now generally believed that it is 
these poisons which produce such grave symptoms in infectious diseases 
rather than any other vital manifestation of bacterial growth. In the 
spring and summer of 1886 Sirotinin made some experiments {Zeit- 
scliriftfUr Hygiene^ I, 403) with the bacillus of typhoid fever, in which 
he endeavors to show that the smaller experimental animals can not be 
infected by this bacillus, but that death caused by injection, subcuta- 
neously or otherwise, must be attributed to an intoxication caused by the 
presence of a ptomaine in the cultures. The results actually proved 
that the injection of sterilized cultures may produce death accompanied 
by lesions resembling those produced by living bacilli. Beumer and 
Peiper {Zeitschri/tfilr Hygiene, II, p. 110), after a long series of experi- 
ments, are brought to the same conclusion, that the typhoid-fever or- 
ganism does not multiply in the body of smaller experimental animals, 
that there is, indeed, no true infection, and that the severity of the symp- 
toms depends entirely upon the quantity of culture material injected; 
in other words, upon the quantity of the poison or ptomaine therein 
contained. They also point out the important fact to which we wish 
to call attention, that death does not follow the injection of large doses 
if small non-lethal doses have been given previously, and from this 
fact they argue that perhaps immunity may finally be brought about 



155 

by the iujectioii of sterile cultures in successively larger doses. That 
tbe chemical products of bacterial growth may produce immuuity is uo 
new theory, but it seems to have gained ground but recently among in- 
vestigators. 

TESTS WITH STEEILIZED CULTURES ON PIGEONS. 

In our experiments iiigeons were selected at first, because more easily 
obtainable and manageable. They iiroved, however, a very good choice, 
since they do not take the disease readily and thus are made insuscepti- 
ble by small doses of culture liquid. A culture in beef infusion, con- 
taining 1 per cent, peptone, in which active multiplication of bacteria 
ceases in a few days, is fatal to adult pigeons, as a rule, when three- 
fourths of a cubic centimeter is injected subcutaneously over the pec- 
toral muscle or superficially into the muscle itself. The intra-muscular 
injection is more rapidly fatal. The effect of these inoculations has 
already been dwelt upon, but it is restated here on account of the im- 
portant i)rinciple involved. 

The pigeon, after such an Injection, may be dead within tweuty-four 
hours. The inoculated pectoral muscle is more or less discolored 
throughout its depth. There may be a regurgitation of food from the 
crop, as grains are found mixed with mucus in the mouth and cesoph- 
agus. The injected bacteria are present in small number in heart's 
blood, liver, and spleen. 

About one half of the pigeons do not die so soon. The bird stands 
quietly in a corner of the coop, with feathers ruftied, wings slightly 
separated, and tail feathers drooping. The discharges are usually ab- 
normally liquid, at times mixed with considerable mucus. The bird 
usually dies within a week. The pectoral muscle will then be found 
extensively necrosed, the surrounding tissue very hypertemic. The in- 
jected bacteria are found, sometimes in considerable number, in the 
liver and heart's blood. 

The rapidly fatal cases might be regarded as the result of simple 
intoxication or ptomaine poisoning. There is, however, some bacterial 
multiplication. In the more chronic cases there is an undoubted infec- 
tion, characterized by multiplication of bacteria in the internal organs. 
Pigeons are far more susceptible in winter than in summer, conse- 
quently in the heat of midsummer the control animals occasionally 
resist and thus imj)air the value of the experiments. 

The experiments were carried out as follows: 

Culture tubes containiug about 10 cubic centimeters of beef infusion 
with 1 per cent, peptone were inoculated with hog cholera bacteria and 
placed in the incubator at 340-30° C. After a certain number of days, 
varying from three to ten, the tubes were exposed to a temperature of 
58O-G0OC. for about one hour. Inoculation of fresh tubes showed that 
bacteria had been destroyed. This test was always resorted to to make 
sure that no living bacteria were injected. 



1.5G 

From 1 to 1.5 cubic centiuiieters of this culture liquid were injected with 
a hypodermic syriuge beueatli the skiu of one pectoral muscle. This in- 
jection was repeated once or twice. Some days after the last injection 
the bird was inoculated with living bacteria. About f. cubic centimeter 
of a beef infusion peptone culture was injected beneath the skin of the 
other pectoral or into the superficial layer of muscular fibers. The vac- 
cinated pigeons remained alive and well 5 the control pigeons nearly all 
died. These statements are best illustrated by the tabulated results of 
a few experiments. 

The first one, made in January, 18SG, is given below. The control 
bird and the one which had received a very small quantity of sterile 
culture liquid died within two days after the test inoculation ; the rest 
were well more than a week later. 



I.— 1885-"86. 



No. 


Injection of— 


Eemarks. 


Sterilized culture liquid. 


Culture 
liquid con- 
taining 
living 
bacteria. 


Dec. 24. 


Jan. 21. 


Jan. 29. 


Feb. 6. 


Total. 


Feb. 13. 


10 
11 
12 
13 
8 
14 


c.c. 

.4 

.8 


c. c. 
1.5 
1.5 
1.5 
1.5 


c.c. 
1.5 
1.5 
1.5 


c.c. 
1.5 
1.5 
1.5 
1.5 


c. c. 
4.9 
4.5 
4.5 
3. 
.8 


c.c. 

i 
f 
f 

a 

a 

1 


Well February 20. 

Do. 

Do. 

Do. 
Died in forty-eight bours. 
Died in twenty-four hours. 



















A second series of injections, made to confirm these rather remarkable 
results, was equally unequivocal in its answer; 



II.— 1886. 



No. 


Subcutaneous injection of — 


Remarks. 


Sterilized culture liquid. 


Fresh cult- 
ure liquid. 


Feb. 19. 


Feb. 24. 


Mar. 2. 


Total. 


Mar. 8. 


16 
17 
18 
19 
20 
21 
22 
23 
24 


c.c. 
1 

1 
1 
1 
1 

1 


c.c. 

1 

1 

1 


c.c. 

I 


c.c. 
2| 
3 
3 
2 
2 
2 


c.c. 

% 

3 
1 
i 
i 

a 


Well after several weeks. 

Do. 

Do. 

Do. 

Do. 

Do. 
Dead Miirch 9. 

Do. 
Remained well. 
















1 
1 



















157 



The third coutrol bird CSo. 24) was of a dififereut race of pigeons. A 
good authority consulted at the time regarded it as having some of the 
characters of the carrier pigeon. Leaving this aside, the result is suf- 
ficiently convincing. 

In a series of experiments made more recently, cultures were used 
which had been concentrated by evaporation in vacuo. About 100 cubic 
centimetersof beef infusion, containing 2 percent, peptone and one-half 
per cent, sodium chloride, was inoculated and kept in the incubator for 
five days. It was then reduced to 20 cubic centimeters by evaporation 
at 40° C, and sterilized at 00° C, for three-quarters of an hour. Sub- 
sequent inoculation of fresh tubes showed that the liquid was free from 
living bacteria. The injections were made as usual, the needle entering 
the pectoral muscle very superficially. 

. III.— 1887. 



No. 


Sterilized concentrated culturo 
liquid. 


FiPsli 
culture. 
li<iuid. 


Kemarks. 


Apr. 19. 


Apr. 22. 


Equivalent 

of ordi- 
nary eult- 
ure fluid. 


Apr. 25. 


1 
2 
3 
4 
5 

7 
8 
9 


c.c. 

i 

i 
1 

1 
1 


c.c. 

i 


c.c. 

2i 

24 

2^ 

5 

5 

5 


c. c. 

i 
i 
I 

3. 

f 
1 

i 
1 


Well May 31. 

Do. 
Slightly ill April 26; well May 31. 
Well May 31. 

Do. 

Do, 
Died April 26, 9 a. m. 
Died April 26, 1 p. m. 
Died April 30. 



























In order to determine whether the introduction of sterilized culture 
liquid into the digestive tract of pigeons would be equally efficient in 
giving them immunity, three pigeons were fed on three daj's (Septem- 
ber 8, 10, 13), each receiving about 30 cubic centimeters in all. The cult- 
ure liquid consisted of beef infusion, to which 1 per cent. i)eptone had 
been added. The feeding was carried out by introducing a catheter into 
the pigeon's crop and injecting through this by means of a syringe. On 
September IG, three days after the last feeding, these three pigeons and 
two checks were inoculated with :| cubic centimeter of unattenuated 
culture liquid. The three fed pigeons and one check died from the ef- 
fects of the inoculation, the second check was well September 29. Tbe 
blood and liver of No. 1 were examined by adding a few loops of heart's 
blood and a minute piece of liver tissue to two roll-cultures. In each 
about 50 colonies developed. In the liver of No. 2 bacteria were very 
numerous. The feeding therefore had no effect whatever in conferiing 
immunity. 



158 

IV. 



Fed with sterilized cultures five 
days and nine days old. 


Inoculation of 
nnbeated 

culture liquid 
Sept. 16. 


Kemarka. 


Ko. 


Sept. 8 


Sept. 10 


Sept. 13. 


1 
2 
3 
4 
5 


c. c. 

10 

10 
10 


c.e. 
10 

10 

10 


c.c. 
10 

10 

10 


c. c. 

1 

i 

a 

3 


Dead September 17. 
Dead September 23. 
Dead September 24. 
Died September 19. 
Well September 29. 















The protected pigeons very rarely show any signs of illness. They 
are as active and as eager for food as before the final inoculation. In 
all a small sequestrum is formed in the pectoral muscle, where the 
injection has been made, and this, at the end of a few weeks, is sur- 
rounded by a dense membrane which seems to act as an absorbing 
surface for the sequestrum. No indication of any reaction is found on 
the side into which the sterile cultures are injected. The three tables 
may be summarized as follows : Of twenty-four pigeons sixteen received 
sterilized cultures, eight being reserved as checks. Of the former none 
succumbed to the final inoculation ; of the latter seven, or 87.5 per cent. 

The conclusion to be drawn from these experiments is obvious. The 
birds are protected by the injection of sterilized cultures so as to resist 
a fatal dose of living bacteria. The sterilized cultures contain only the 
products of bacterial growth. Among these the ptomaine-like bodies- 
some of which we now know, owing to the researches of Brieger— are 
very likely the agents that produce immunity. 

In the pigeon the mode of infection before and after vaccination is 
probably as follows : The injected bacteria multiply very actively in the 
muscular tissue; the ptomaines there produced may enter the circula- 
tion in quantities large enougb to produce speedy death. If the animal 
resists for a time, the absorbed ptomaine reduces the vitality of the 
tissues to such a degree that bacteria, entering the circulation, begin 
to multiply in the internal organs. The additional quantity of ptomaine 
thus i^roduced finally kills the bird. 

When ptomaines in culture liquids have been previously introduced 
the first shock caused by the local production of ptomaines in the mus- 
cular tissue is overcome. The bird resists successfully general infec- 
tion until the bacteria have been destroyed locally. The process is then 
checked, and the sequestrum in the muscular tissue becomes encysted. 

It has already been stated (p. 69) that rabbits, mice, and guinea-pigs are 
very susceptible to the inoculation disease, a millionth of a cubic centime- 
ter of culture liquid being sufficient to cause a fatal issue. Experiments 
like those on pigeons were made upon rabbits with slightly larger doses, 
but no immunity was gained thereby. The rabbits succumbed invariably 
after inoculation. (See report of Department Agricult-ure for 1886, p. 



159 

637.) In the light of later experiments* made iu Pasteur's laboratory, 
the failure of the method iu case of rabbits must simply be ascribed to 
the small quantity of culture liquid used. In the experiments there re- 
corded from 80 to 120 cubic centimeters of culture liquid were required 
to protect guinea-pigs from malignant oedema, while in our rabbit ex- 
periments only 5 to 6 cubic centimeters were used iu all. We did not 
delay, however, with the further demonstration of this principle upon 
small animals, and applied it experimentally to pigs. The quantities 
injected were not sufiQcient, however, and the animals took the disease, 
as the following experiments show: 

TESTS WITH STERILIZED CULTURES ON PIGS. 

Experiment 9. — In order to test the effect of heated cultures upon 
pig!?, the following experiments were made March 1 : Two animals (l^os. 
1G2 and 173) received hypodermicallj'^ each 9 cubic centimeters of a sec- 
ond and third culture, twelve and thirteen days old, respectively, which 
had been devitalized by heat. March 9 a second dose of 9 cubic centi- 
meters was given in the same way, using a fifth and eighth culture 
eighteen and fourteen days old, respectively. These cultures were 
made in beef infusion containing 1 per cent, peptone, excepting one, 
which contained about 2 per cent, of blood serum in place of the pep- 
tone. After the second inoculation of No. 162 a swelling appeared on 
one side. Both were fed with viscera infected with hog cholera, and 
placed with sick and dying pigs in a large infected pen. No. 162 was 
found dead March 29, and No. 173 April 5. The appended table and 
notes give a summary of the experiment : 



No. 


Mar. 1. 


Mar. 9. 


Total. 


Fed. 


Died. 


No. of days 
after feed- 
ing. 


162 
173 


c.c. 
9 

9 


c. c. 
9 

9 


c. c. 

18 

18 


Mar. 19 
Mar. 19 


Mar. 29 
Apr. 5 


10 
17 



No. 162. Subcutaneous fatty tissue much reddened. Mucous mem- 
brane of stomach considerably ulcerated ; mucous membrane of small 
intestine deeply congested. For 8 or 10 feet above the ileo-caical valve 
the mucous membrane of ileum is completely necrosed. Large ulcers 
in c?ecum and upper portion of colon. 

No. 173. Subcutaneous fatty tissue slightly reddened. Petecchije un- 
der pulmonary pleura. Extravasations under serosa of ctECum and 
colon. Inflammatory adhesions of large intestine with walls of abdo- 
men. A patch of extravasation beneath peritoneal layer of dorsal ab- 
dominal wall nearly 2 inches across. Spleen very much enlarged and 
softened. The mucous membrane of large intestine and several feet of 
ileum necrosed and breaking down. Fundus of stomach deeply con- 
gested. 

This experiment clearly showed that this method was no protection 
to the animal when the latter was infected by feeding. 

*Annales de VInstitut Pasteur, December, 1887, Jauuary, 1888. 



160 



It now became necessary to determine whether this method -would 
confer immunity upon animals simply exposed to the disease by cohab- 
iting with diseased animals in infected pens. Observations made upon 
other diseases by investigators, and by us upon this disease, seem to 
lead to the inference that it frequently depends on the quantity of virus 
introduced into the system whether the disease will make its appear- 
ance or not. In feeding, this quantity is considerable; in simple ex- 
posure in infected pens to diseased pigs, the amount of virus taken into 
the body with the food and drink is necessarily in small and repeated 
doses. The following was therefore planned : 

Experiment 10. — Four pigs ([N'os. 163, 1G4, 177, and 196) were iuocu. 
lated March 13 with heated virus, each receiving 4i cubic centimeters 
beneath the skin of each thigh. The cultures in beef infusion with 1 
per cent, peptone were about fifteen days old when heated. The second 
inoculation was made March 16 from a culture in an Erlenmeyer flask 
about eleven days old, and containing about 50 cubic centimeters of 
culture liquid. Each animal receiv^ed 10 cubic centimeters as before. 

March 31 these animals, together with two check pigs (Nos. 195 and 
201), were placed in a large infected pen. Within a period of three 
weeks from this date at least fifteen pigs died of hog cholera in this 
pen. The two check animals died on the 14th and 19th of April, re- 
spectively. Of four vaccinated animals only No. 163 showed signs of 
the disease and gradually developed into a chronic case, dying of general 
debility on May 1, The three other vaccinated animals remained ap- 
parently well for months after, although constantly exposed to the dis- 
ease in the infected pen. 



No. 


VacciDation. 


Exposure. 


Died. 


Number days after exposure. 


Mar. 13 


Mar. 16 


163 
164 

177 
196 
195 
201 


c. c. 
9 

9 

9 

9 


, e. c. 
10 

10 

10 

10 


Mar. 31 


May 1 


Thirty-oce days. 

Tliree months and twenty-three days. 
Three months and seven days. 
Nineteen days. 
Fourteen days. 


Mar. 31 
...do.... 
. . do ... . 


July 23 
July 7 
Apr. 19 
Apr. 14 






. do 









Autopsy notes. — No. 163. Spleen not much enlarged ; texture firm ; 
effusion into pericardial and thoracic cavity; lymphatic glands enlarged, 
but pale; two ulcers in stomach; small intestine normal; mucosa of 
cpecum and colon studded with many extensive and deep, yellowish 
ulcerations. On cover-glass preparations of the spleen only a few bac- 
teria could be seen. Two liquid cultures inoculated from tlie same organ 
remained sterile. No colonies appeared in the gelatine tube inoculated 
witli blood from the heart. A few developed in the gelatine tube inoc- 
ulated from the si)leen. 

No. 195. Spleen greatly enlarged; gorged with blood; very friable; 
shreds of a fibrinous exudate on serosa of intestines ; much serum iu 
abdominal cavity; petecchia3 on epicardium of auricles; small ventral 
lobes of lungs hepatized ; mucous membrane of gall bladder ulcerated j 



161 

exteusive ulceration and iuflaniniation of mucous membrane of ctecum 
and colon. Hemorrhagic inflammation of kidneys. 

No. 201. Spleen but slightly enlarged ; lungs extensively hepatized ; 
intense congestion and commencing ulceration of the mucosa of largo 
intestine; stomach and portion of ileum similarly congested. Though 
uo bacteria were found on a cover-glass preparation, a pure culture was 
obtained by carefully dropping a piece of spleen tissue into a culture 
tube. This was tested on gelatine. 

Alter apparently resisting the infection for several months, the remain- 
ing i)igs (Nos. 1G4, 177, and 19G) were transferred to a clean pen. No, 
177, not very thrifty, began to decline, and finally died July 23. Among 
the most i)rominent lesions were a plastic exudate on the cpicardium 
and numerous large old ulcers in the large intestine. The mucosa itself 
was extensively pigmented. No. 196, on removal from the infected pen, 
seemed in good condition, but it died July 7, alter some days of 
unthrifty condition. In this case, the mucous membrane of the large 
intestine was pigmented and there were what appeared to be cicatrices 
of old ulcerations. In all of the large serous cavities there was con- 
siderable effusion. In cover-glass preparations of the spleen there were 
no hog cholera bacteria to be seen, but numerous bacilli resembling 
those of malignant (tdema. 

Experiment 11 was made in the same way upon Nos. 197 to 200, in- 
clusive, and No. 157. March 21 each animal received in the thigh about 
10 cubic centimeters of a mixture of heated cultures in beef infusion with 
1 per cent, peptone about fourteen days old. March 29 an equal amount 
was injected, one half into each axilla, these cultures being about fifteen 
days old. These animals were kept until April 20, when all but No. 157 
were placed in the large infected pen. From that date on pigs died almost 
every day of the disease, so that the infection must have been quite 
thorough. Unfortunately no check animal was exposed at the same 
time. In these animals the slight swelling at the seat of inoculation 
disappeared in a few weeks. 

They remained well, with the exception of No. 199, which became 
eumciated and was found dead May 19, about one month after exposure. 
The three remaining animals were apparently unaffected nearly two 
months after exi)0sure. At this time No, 197, which appeared rather 
thin, was killed, to determine if any ulcerations were present. But the 
mucous membrane of the intestine was entirely normal, with no indi- 
cations of former ulcerations. 



No. 
197 


Injection of heated 
virus. 


Time of 
exposure. 


Eemark.«. 


Mar. 24 

c.c. 

10 


Mar. 29 


c.c. 

10 


Apr. ':o 


Killed June 10; 










Iiealthy. 


198 


10 


10 


...<lo... 


Well Juue 10. 


199 


li) 


10 


...do .... 


Died May 10. 


200 


10 


10 


...do.... 


Died July 12. 


157 


10 


10 


May 25 


Died June 28. 



15012 II c- 



-11 



162 

Autopsy. — No. 199. Slight extravasation iu subcutaneous connective 
tissue. Spleeu somewhat enlarged, filled with blood, triable; consider- 
able effusion in peritoneal cavity. Eight Inng in part hepatized ; pleu- 
ritic adhesions to chest-w^all; hemorrhage in and about i)elvis of kid- 
neys; lymphatic glands purplish ; extensive and deep ulceration of the 
mucosa of large intestine. 

Pig 197, killed for examination, was very anaemic. There was some 
l)ale serum in abdominal cavity. The kidneys and lym[)hatic glands 
showed evidence of chronic inflammation. The lungs were exceedingly 
pale. No evidence of inflammation or ulceration in any portion of the 
intestinal tract. 

It must be borne in mind that these animals were constantly exposed 
for a period of several months to the virus of the disease, aud that a 
continual struggle between the organism aud the invading parasites 
must have been going on, which naturally would tend to lower the vi- 
talit3\ Such severe conditions as these are probably never realized 
among herds. 

The later history of No. 200 does not, however, bear out the first 
supposition that complete immunity was attained. After being contin- 
ually exposed in the infected pen iroin April 20 to June 21 it was re- 
moved to a clean pen, where it continued to grow very weak. It died 
July 12. The autopsy revealed a plastic pleurisy over the right lung 
aud a fibrinous exudate upon the epicardium. The mucosa of the etecum 
was extensively necrosed ; iu the colon the ulcers were isolated ; the 
solitary follicles were very prominent. A small bit from the epicardial 
exudate was placed beneath the skin of two mice. One of them died 
on the eighteenth day. The spleen was greatly enlarged. Numerous hog 
cholera bacteria were present in this organ and the liver. The epicard- 
ial exudate of the pig must have contained but very few, for they could 
not be demonstrated in cover-glass preparations. The long period of 
time from the inoculation of the mouse to its death is also evidence of 
a very small quantity of virus. 

No. 157, inoculated with the rest, became quite lame in the hind limbs, 
so that it was thought best not to expose it to the disease in the infected 
pen for the time being. It soon recovered its power of locomotion, and 
was transferred to the infected pen May 25 aud removed therefrom 
June 28. In the new pen it grew rapidly weaker, and died June 28. 
On postmortem examination the right lung was found entirely hepatized 
and adherent to the chest- wall. The mucosa of c;ecum and colon was 
studded with large and deep ulcers; that of the fundus of stomach was 
deeply congested. 

Experiment 12. — It became desirable to determine whether repeated 
subcutaneous injections of heated cultures, until a large amount had 
been introduced into the system, would be more efficacious in produc- 
ing immunity. For this purpose the culture liquids were concentrated, 
by using a 2 per cent, solution of meat extract with 2 per cent, peptone 
for some of the injections; for the remainder a 2 per cent, solution of 



163 

peptone in beef infusion. Tlie cultures were made in Erlenraeyer flasks, 
l)lngged with cotton wool. 

The table g'iven below ^nves the date of the injection and the (jnan- 
tity used each time. It will be noted that Nos. 191 and 194 received 
two, Nos. 2IG and 218 three, and Nos. 217 and 221 four doses eacii ot 
the heated culture liquid. The injections were made two days apart, 
the exposure in the infecte<l i)en and among diseased animals about one 
week after the last inoculation. Nos. 220,232, and 235 were placed in the 
infected pen at the same time, to determine the virulence of the infec- 
tion U|ion pigs which had not received any injection. 



No. 


Heated virus. 


Total. 


Exposure 
in infect- 
ed pens. 


Rcniaik.s. 


Apr. 20. 


Apr. 22. 


Apr. 24. 


Apr. 26. 


?.1G 

217 

218 

221 

191 

191 

*220 

*232 

*235 


c. c. 
9 

9 

9 

9 


c.c. 
8 

8 

8 

8 


c.c. 

10 
10 


c. c. 


c.c. 
24J 

32J 

24i 

32^ 

18 

18 


May 4... 
...do .... 
...do .... 
...do .... 
...do .... 
...do .... 
do 


Died ^lay 17. 
Died May 19. 

Do. 
Died May 23. 

Do. 
Died May 19. 
Died May 17. 
Died May 23, 
Died June 12. 


8 


8 
8 
8 




















.. do ... 












...do ... 















* Checks. 



All of the inoculated and control animals died with periods ranging 
from thirteen to nineteen days, only one living thirty-nine days, and 
this one a control animal. Of those that had received two doses, No- 
191 died May 23 (nineteen days after exposure) with considerable ul- 
ceration in cfecum and colon. No. 194 died May 19, with extensive and 
deep congestion of the lymphatic glands in general, of the kidneys, 
stomach, and large intestine. In the latter, ulceration was not yet be- 
gun. No. 210, which had received three doses, died very unexpectedly 
thirteen days after exposure. The lesions were of the liemorihagiii 
type, involving extravasations and ecchymoses of the intestinal tract, 
more especially of the large intestine, heart, lungs, lymphatic and sub- 
cutaneous fatty tissue Ulceration in large intestine very slight, the 
congestion being intense. No. 21S, treated like the former, died fifteen 
days after exposure. The lesions were like those of No. 210, but not so 
severe. Ulceration as yet very slight. 

Nos. 217 and 221, which had received four injections, died fifteen and 
nineteen days after exposure, respectively. The lesions in No. 217, 
which died very suddenly, were hemorrhagic in character, the ulcera- 
tion in the ctiecum and colon being quite superficial. In No. 221 the 
ulceration was more pronounced, the general congestion and extrava- 
sation much less so. 



164 

Of the control aiiiaials the lesions of No. 220 wereof the heniorihiigic 
type, lesembliug- those of No. lOi very closely. lu No. 232 there was 
extensive ulceration of the mucous membrane of the large intestine. 
In No, 235, which lived for thiityuine clays after exposure, the mucosa 
of t^e caecum and upper portion of the colon was involved in complete 
necrosis nearly 5 millimeters thick. Beyond this the necrosis took the 
form of isolated ulcers. Owing to the depth of the ulceration inflamma- 
tory adhesions had formed between the ciecum aud adjacent organs. 
There was uo reactionary swelling of the inoculated animals at the 
point of injection. 

Those animals in which the disease took the hemorrhagic type suc- 
cumbed very suddenly, as if the invasion had taken place in a single 
day. In those animals in which symptoms of weakness and loss of ap- 
petite appeared some days before death the well-defined lesions were 
as a rule limited to the large intestine in the form of nlcer.itions. The 
former cases represent a class in which the bacilli invade the entire 
vascular system ; in the latter the absence of a general congestion aud 
extravasation seems to indicate a more local multiplication of the spe- 
cific disease germs in the intestinal tract. 

This mode of vaccination, as shown by the results recorded, did not 
])rove to be any protection to the animals, as they died, most of them, 
within a brief period after exposure from a very acute attack of the dis- 
ease. 

The spleen examined in about one-half of these cases contained the 
bacillus of hog cholera, usually in large uuaibers. From a few cultures 
were made which were found pure. 

Experiment 13.-rA final experiment was tried in which each animal 
received hypodermically 40 cubic centimeters of heated culture liquid 
in two doses. The cultures were nuule in beef infusion with 1 per cent, 
peptone, the growth being killed by a temperature of 58° C. the third 
day after inoculation. The llasks used were shaped like Erlenmeyer 
flasks, a glass cap being- fitted over the flask by means of a ground-glass 
joint, which contracted into a straight narrow tube plugged with glass 
wool. The removal of a cottonwool plug was thus avoided, the 'cap 
being removed for inoculation. This culture flask aflbrds better venti- 
lation and a more rni)id evaporation of the culture liquid than does the 
culture tube with the bent ventilating tube. 



165 

Tlic following- tab'o gives ail the facts necessar3' for an uiulerstand- 
iiig' of tbe experiment aud its results : 



No. 


Heated viru.s. 


E-xpos- 

urein 

infected 

pens. 

June 21 
. . do , . . 
...do ... 
. .do ... 
..do ... 
...do ... 
...do ... 
...do .... 


i;piiiarks. 


Days after 
first ex- 
posure. 


June 14. 


June 17. 


231 
233 
2CC 

*230 
21)7 
268 
260 

*270 


e c. 

20 
13 
20 

20 
20 
20 



c. c. c. c. 

20 40 
20 33 
20 ; 40 

20 -10 
20 40 
20 40 



Died July 7 . 
Died July 0. 

... do 

Died July 8 . 
Died July . 
Died July 10 

. . do 

Died July 9... 


16 

18 

18 i 

17 

15 

18 j 

10 

18 



* Cbeclis. 

It will be seen that all the experimeDtal aiiiiuals died, inoculated aa 
well as check animals, within a few days of one another, death taking- 
place abont sixteen to eighteen days"after the first day of exposnre, A 
brief synopsis of {he iwst mortem appearances will not be amiss in this 
connection. 

In N"o, 231 the spleen was very mnch enlarged aud gorged with blood. 
The intensely congested mncons meiid)raue -of the ctecum and colon was 
dotted with small superficial ulccratious. In No. 233 the congestion of 
S[)leen, and ulceration with congestion of the large intestine, vrere also 
marked. Xo 200 presented the same lesions. The ulcers in the caecum 
wTre fron one-quarter to one half inch across No. 230 (check) dift'ered 
from the preceding cases in presenting severer lesions, greatly enlarged 
and congested si)leen and lymphatic glands, sni)erficial necrosis of the 
entire colon and great thickening of tlie walls, extensi\c extravasa- 
tion of blood lieneath the mucosa of duodenum. 

Of the second lot of four, treated in the same way, No. 207 presented 
very severe lesions, consisting of intense congestion and extravasation, 
involving the spleen, lymphatic glands, lungs, and kidney. The left lung- 
was adherent to costal i)leura. There was considerable hemorrhage in 
the pelvis of both kidneys. The large intestine was least changed, the 
mucosa being slightly ulcerated aud containing some hemorrhagic spots 
and points. This animal was first to die out of this lot of eight. In No. 
208 the congestion involved the lymphatic glands generally and the 
mucosa of the Inrge intestine, which was extensively necrosed in its 
upper portion. No, 209 resembled No. 207 in the severity of the lesions. 
The lungs were not •affected, however, while the nh oration of ca3cum 
aud upper colon was very extensive and deep. No. 270 (check) pre- 
sented extensive ulceration of the large intestine and a greatly enlarged 
spleen. In five cases the spleen contained the bacteria of hog cholera 
more or less abundantly. In two none could be seen on one or two 
cover-glasses. No local swelling had developed at the points of injec- 
tion in any of the inoculated animals. 

The quantity of culture liquid in those cases was likewise too small to 
have any beneficial effect. Experimeiits are now being pro.secuted in 



1G6 

the same direction by injocting very large (]nantities. These are, how- 
ex ei-, nut coini)lete(l. 

Tlie experiments on tlie use of sterilized cultures have thus not be- 
come practically applicable as yet. The great importance of this prin- 
ciple, however, has been duly appreciated ^Yithin the past year in foreign 
countries, notably in France, where experimentation of this kind has 
been curried on by pupils and assistants of Pasteur. The principle is 
destined to be serviceable in other infectious diseases, ami may eventu- 
ally take the place of the older methods of Pasteur which utilize attenu- 
ated cultures of bacteria. These are often sufficiently virulentto destroy 
slice]) (anthrax), and in this way may themselves become the agents 
that distribute the disease. For this reason anthrax vaccination is only 
practiced in those regions where the disease is more or less endemic, and 
where the losses exceed a certain percentage each year. 

Chantemesse aiul Widal* have recently endeavored to set aside the 
claim of the Bureau of having first demonstrated this principle, in favor 
of the more recent researches made in Pasteur's laboratory. Hiippel 
has, however, siiown the absurdity of this claiui in pointing to the ex- 
periments of the Bureau as having been published nearly two years 
prior to those of Chauiberland and K'oux. 

* Annales'de VInstifnt Pasteur, February, 1888. 
i Fortschritle der Medichi, 1888, 289. 



EXPERIMENTS ON THE ATTENUATION OF HOG CHOLERA BACILLI 

BY HEAT. 

Heat bas been used by Pasteur iu tiie attenuatiou of autbrax virus 
by exposing cultures of antbrax bacilli to a temperature of 42*^-4:3° C, 
continuously for a certain number of days. Cultures kept in a tliermo- 
stat at tbis temperature for about tliirtyonc days were so attenuated 
tbat tbey were incapable of destroying animals larger tban very young 
mice. Kept in tbe same conditions for only twelve days inoculation 
failed to destroy adult guinea-pigs.* Tbe former culture was denomi- 
nated tbe first, tbe latter tbe second vaccine. To make sbeep immune 
tbey were inoculated subcutaueously witb tbe first vaccine, twelve days 
later witb tbe second vaccine. Subsequent inoculation witb strong virus 
bad no effect upon tbe vaccinated animals, altbougb it was quite inva- 
riably fatal to tbose wbicb bad not been so treated. 

Altbougb Pasteur's discovery must be considered a scientific event 
of great importance, its practical application is by no means a perfect 
success. Experiments conducted by Kocb, Gafifky and Loftier, in Ber- 
lin, bave sbown tUat tbe process of attenuation does not always go on 
uniformly, and tbat tbe strengtb of tbe vaccine can not always be relied 
upon. A few animals may die as a result of tbe first or second inocu- 
lation. Tbis fact induced tbe last International (congress of Hygiene 
at Vienna to adopt tbe resolution tbat antbrax vaccination sbould not 
be practiced upon sbeep in any locality unless tbe disease causes a loss 
of 2 to 3 per cent, annually. It was also sbown in tbe experiments at 
Berlin tbat immunity after vaccination is not absolutely perfect wlien 
tbe virus is introduced witb tbe food. Tbis is perbaps tbe most com- 
mon way in wbicb infection takes place. 

Tbe results obtained by Pasteur are sufticiently valuable to make it 
at least desirable to try beat attenuation for otber bacterial organisms, 
altbougb it does not follow by any means tbat tbe same process will 
sufiice for all or even a small number of disease germs, for tiiese differ 
among one anotber very widely. 

Kitt* bas tried beat in tbe attenuation of tbe virus of Black Quarter 
in Germany by exposing tbe diseased muscular tissue, wbicb bad been 
tborougbly dried in tbe air and ground to a fine powder, to tbe steam of 
boiling water at 100° C. for four, five, and six bours continuously. 
Tbe spores of tbe bacilli of tbis disease were sufticiently attenuated after 
a six-bours' exposure tbat sbeep inoculated witb tbe powder in certain 
doses remained well after inoculation v>'itb strong virus. The reaction 

* Comi)t. rend. Acad, des Sciences March 21, 1881. 
*CentraJbl. f. Bakteriologie und I'arasitenlunde, 1888, i. 571. 

167 



168 

after the vaccinal inoculation was very slight. Hog cliolera virus is 
destroyed by a fifteen to twenty minutes' exposure in a water-bath at 
5S^ C. ; a momentary contact witli boiling water is sufficient to destroy 
it, so that Kitt's method is not applicable to it, but only to bacteriii 
which form spores. 

The following experiments were undertaken with a view to test the 
method of Pasteur on hog cholera bacilli, and to obtain, if possible, a vac- 
cine similar to that employed in the prevention of anthrax. Although 
only a preliminary step has been taken in this matter, and the promise 
of favorable results is not tiattering, we consider it best to publish the 
results thus far obtained. 

The first step in the process was to obtain, if possible, a cultivation 
which should prove harmless to rabbits. This was to be accomplished 
by placing tubes in a thermostat, kept at a certain fixed temperature as 
nearly as possible, and inoculating rabbits from time to time to deter- 
mine anjf diminution in the pathogejiic activity. 

April 9, 1888. — Four Salmon tubes of beef infusion peptone were in- 
oculated from an agar agar culture of hog cholera bacilli two weeks old 
and j)laced in a d'Arsonval thermostat, the internal temperature of 
which registered between 42° and 43° C. Two series of inoculations 
were made on rabbits, one from one of the original liquid cultures at 
different intervals, the other from a culture renewed at the end of every 
five days by inoculating a fresh tube. The result is most easily under 
stood by examining the following table: 

Agar culture. 



Apr. 19, rabbit 
Apr. 25, died. 



inoculated 



Apr. 30, rabbit. 
May 4, died. 



May 9, rabbit. 
May 18, died. 



Apr. 0, b. i. p. *(a). 



Apr. 14, b. i. p. (a,)- 



Apr. 19, b. i. p. (a,,). 



Apr. 24, b. i. p. (a^) 



Apr. 30, 1). i. p. (ai). 



May 4, b. i. p. (ar,; 



May 9, b. i. p. (an). 



Apr. 19, rabbit inoculated. 
Apr. 24, died. 



Apr. 30, rabbit. 
May 5, died. 



May 9, rabbit. 
May 10, died. 



Beef inlusiou phi.s 1 per cent, peptone. 



169 

The first inoculations were made April 10, with culture «, wliicli had 
been in the thermostat ten days, ar,d culture <iu which had been freshly 
made on April 14. Both rabbits received about -} cubic centimeter of the 
culture liquid hypodermically. Rabbit Ui died in five days with extensive 
coagulation necrosis in liver and enlarged s[)leen. Ivabbit a died on the 
following day with the same lesions. In both hog choler.x bacilli were 
very numerous on cover-glass preparations of S])leen, and obtained i)ure 
in cultures. The same results were obtained in all subsequent cases, 
so that no further mention need be made of this. 

Two rabbits were inoculated in the same way Ai)ril 30, one from the 
original culture a, the other from <?> Both died May 4 and 5, respect- 
ively. Lesions the same as with the first pair. 

Two rabbits were inoculated May 9, one from the culture «, now thirty 
days old; the other from ^^-,, the fiftii renewal of a. Both rabbits died 
on the 7th and the 9th day, respectively. TIic lesions were itractically 
the same, with the addition of slight hemorrhagic lesions in the iu- 
testinal tract. The period of the disease was slightly prolonged. 

The result was not very satisfactory. If any attenuation was go- 
ing on, its, final attainment would demand too long a i)eriod of time. 
The experiment was therefore stopped and another undertaken. The 
temperature of the thermostat was raised to 45° C, to hasten the pro- 
cess of attenuation. 

^pr. 23, agar culture. 
May 12, b. i. p. (b). 



May 22, rabbit inoculated. May 17, b. i. p. (b')- 

May 29, died. 

May 22, b. 1. p. (b'). 

It was found that cultures inoculated from b failed to develop at the 
assigned temperature, so that this exi)eriraent was not continue*! any 
farther. It deserves to be mentione<l, however, that a rabbit inocu- 
lated from the original culture, which liad been kept at 45° C. for ten 
<lays, died seven days alter inoculation with enlarged spleen and co- 
agulation necrosis in liver. 



170 

A temperature of ^3^-44° C. was iiextclioseii and tlie experiment con- 
ducted in the same maniiei-, as tbe appended table will show : 

(lG3b.) 
May 10, agar lulturo. 

May 20, b. i. p. (a) (.KJfi-iio c.) 



Juno 8, r.ibbit. 
Juno 14, dOr\(l. 



June 18, rabbit. 
June 23, dead. 



June 28, rabbit 
(Remains alive. > 
(Culture dead. 



June 8, rabbit. 
June 15, dead. 



Juno 18, rabbit. 
Juno 24, dead. 



June 28, rabb:t. 
July 5, dead. 



Juno 4, 1). i. p. (a.) 



.June 8. 1). i. p. (fails to 

grow). 



June 13, b. i. p. (aj). 



June 18, b. i. p. (aj) 



Juno 23, b. i. p. (aj). 

(Supposed imiiurf, 

but found pure.) 



June 28, guinea pig. Juno 28, b. i. p. (34). 
July 10, dead. 



July 10, rabbit. -Inly 10, rabbit. 

(Remains alive.) (Uimains alive.) 

May IC, cigar culture. 

May 29, b. i. p. (b) (43io-4<° C.) 

July 14, placed at 3C°-3."o C. 



July 10, b. i.p. (as). 
(Culture dead.) 



July 25, rabbit. 
July 30, dead. 



August y, rabbit. 
(Reuiaina well.) 



August 4, b. i. p. 
(Sterile.) 



171 

The rabbits inoculated from the original culture after remaining at 
the temperature of 43.50-44° (J. for ten and twenty days died from 
the inoculation disease, but those inoculated from the same tube, after 
thirty and forty-three days, remained permanently well. This was not 
due to an attenuation of the culture, but to its death. Turning to the 
series of rabbits inoculated from the cultures renewed every tive or 
ten days, those receiving culture liquid ten, twenty, and thirty day« 
old died from the inoculation disease, while one inoculated after 
forty-three days remained alive, because the culture was dead, i. c, it 
failed to fertilize frrsh tubes after repeated inoculation. An adult 
guinea pig, inoculated from the same culture material, thirty days 
old, died in twelve days as a result of the injection. In this case 
only a few drops had been injected. This experiment demonstrates 
that in general the pathogenic i)ower of hog cholera bacilli is only 
destroyed by the death of the organisms themselves. This is a very 
important fac'. It will be remembered that in the attenuation of an- 
thrax bacilli their virulence was gradually diminished, and a time was 
reached when ihey failed to kill all but mice, while they still retained 
the power of multii)lying in nutritive liquids. In the above experi- 
ments even guinea-pigs, which are less suscei)tible to this disease than 
rabbits, died twelve days before the culture was found dead. The 
latter may have been dead some days before this, for no tests were made 
meanwhile. 

This fact has an important bearing upon the nature of the pathogenic 
activity of hog cholera bacilli. It shows that there are two elements 
involved, (1) the ptomaine action of the organisms; (2) their mechanical 
effect. That there is a ptomaine action of these bacilli has been con- 
clusively proved in the experiments of the Bureau made upon pigeons 
several years ago. But this ptomaine action is evidently secondary to 
the mechanical effect of the bacilli in forming plugs or thrombi in the 
blood vessels and thus causing destruction of tissue by impeding the 
circulation. This tendency to act mechanically is not lost as long as 
the bacilli are alive, as shown by their fatal effect on rabbits and guinea- 
pigs shortly before they themselves are destroyed. 

At the temperature employed (43.50-44o C), the original bouillon- 
peptone culture a died between the twentieth and the thirtieth day 
after the beginning of the exposure. The culture from this, renewed at 
the end of every lifth or tenth day, died between the thirtieth and 
forty-second day. Another culture b (see table), which had been re- 
moved from the thermostat after the forty-sixth day and kept at the 
temperature of the laboratory (about 300-33° C, during July) was still 
fatal to a rabbit on the lifty-seventh day. Another rabbit, inoculated 
ten days later, remained well, and a fresh culture made at the same 
time remained sterile, showing that theapparent immunity of the rabbit 
was due to the death of the bacilli injected. This experiment also 
shows pretty conclusively that the pathogenic power of these specific 
organisms expires oidy with their life, and not long before. 



172 

It is evident from our own experiments, and more recent ones made 
in France and Germany, conducted on the same lines, tliat the amount 
of immunity which we may expect to gain from preventive inocuhi- 
tion will depend on the quantity of ptomaines produced by the s])ecific 
microbes i. e., upon their poisonous nature. In other words, our suc- 
cess will depend upon the relation borne by the ptomaine to the disease 
process. If this factor is very great it is highly probable that prevent- 
ive inoculation either with ptomaines or with attenuated cultures will 
be successful. But if there is in addition a mechanical element, which 
may or may not overshadow in importance the ptomaine element, the 
problem is not only complicated, but may fail. 

There are two other points in connection with these experiments which 
demand attention. One is the variation in the length of life of the dif- 
ferent cultures exposed to the same conditions. This would be a seri- 
ous hindrance in obtaining vaccinal cultures of uniform strength, should 
this method ever ])rove successful. 

There was a noticeable change in the appearance of the serial cult- 
ures after a sojourn in the thermostat. There was a tendency to mul- 
tiply rather more abundantly, to grow in minute flakes and to rise to 
the surface to form a thin, unbroken membrane. The motility was 
somewhat impaired after a time. These changes gave rise to the sus- 
picion of impurities, but tests on gelatine plates showed that the sus- 
picion was unfounded. These experiments will be continued on pigs 
under similiar conditions to determine whether any immunity can be 
produced by this method. 



HOG CHOLERA, OR DISEASES CLOSELY ALLIED TO IT, IN OTHER 

COUiNTRIES. 

GREAT BRITAIN. 

This disease was first detected in 18G2, where it has been known under 
various names, the most common of which is swine fever. Owing to 
the fact that there are recognized at the present time three distinct in- 
fectious diseases of swine in different parts of Europe and America, it 
is impossible to state whether the disease known as swine fever in 
England represents two distinct maladies, hog cholera and swine plague, 
or hog cholera alone. This question can only be solved by a thorough 
bacteriological investigation, such as has not been made there in very 
recent years. There is enough evidence, however, to warrant the state- 
ment that hog cholera is prevalent in Great Britain. There is, on the 
other hand, no experimental basis for the statement that the other dis- 
ease, swine plague, also exists there. These two diseases produce le- 
sions of the large intestine, so easily confounded with each other, that 
great care must be taken in making a diagnosis. We must also con- 
sider that the three well marked swine diseases now known as hog 
cholera, swine plague and roitgct, were only a few years ago regarded 
as one disease designated by a great variety of names; that even to- 
day no clear idea exists among most pathologists as to what the precise 
differences between these diseases are. 

In a brief report on swine fever in Great Britain, by Professor Brown, 
of the Agricultural Department, in 1880, we do not notice that any 
doubt exists in his mind as to the oneness of the disease in Great Brit- 
ain and its identity with hog cholera. He even reproduces a plate from 
the report of the United States Department of Agriculture for 1885, 
in which the characteristic ulcers of hog cholera are shown as an illus- 
tration for his text. 

That there may be several diseases included under the term swine 
fever is evident from tiie statements made in this report concerning the 
annual importations of diseased swine from other countries. Swine 
fever is said to have affected animals imported from Holland, Denmark, 
Sweden, Norway, and the United States. Now, hog cholera appeared 
in the North European countries for the first time in 1887. The swine 
marked diseased may have been affected either with swine plague, 
which exists on the Continent, or with lighter non-infectious forms of 
lung disease not uncommon in pigs at any time in the year. 

173 



174 

We quote, from Professor Brown's report tbose parts wliicb may prove 
iuterestiug- to American readers, using- the languageof the report itself 
whenever possible: 

ISymptoms of su'ine fever. — It is most important that the farmer 
should be acquainted with the signs which indicate the existence of 
swine lever at tlie earliest period of its development ; bnt unfortunately 
the disease is very difficult of detection in the early stage in the greater 
number of cases, and the symptoms which are generally believed to be 
specially indicative of the affection, viz., redness of the skin on certain 
])ortions of the body, and diarrhea of a i)eculiar kind, do not appear until 
the disease is fully developed, and in nnmerous instances are not ob- 
served at all. The animals W^ed fairly well, show no rise of temperature ; 
they are vigorous, and for several days, and even for several weeks, be- 
tray in no way the disease. It requires very careful and prolonged ob- 
servation to notice that at one time or another — at any rate at rare in- 
tervals — the swine have a short cough, not an important departure from 
the healthy state. Very few experts, to say nothing of the owner of the 
pigs, would suspect swine fever because he happened to hear the ani- 
n)als cough at rare intervals; and there is in these mild cases, which 
Dr. Klein considers constitute the majority, absolutely nothing else 
which would be noticed; the ski-n remains quite free from any appear- 
ance of disease. It is true that the inguinal glands are distinctly en- 
larged, but nidess the owner thinks of inspecting these small lymphatic 
glands (kernels) under the skin of the pig's groin, and knows what 
their proper size is in health, he has no chance of recognizing the dise.ise 
in this obscure form. In the organs of these ai)parently healthy pigs 
there are found on dissection very pronounced symptoms of disease, so 
pronounced in fact, that it seems astonishing that during life the ani- 
mals presented such slight signs of it. And these very slight signs, it 
may be remarked, were only noted by the observer in the cases of pigs 
which were under constant observation after they had puri)osely been 
infected with the disease. 

Swine which are affected with swine fever in the occult form may 
be moved about freely, sent to market, bought and sold over and over 
again, distributing the infection wherever they go, without exciting the 
least suspicion in the minds of those who buy or sell or keep them that 
they are infected with a deadly and highly contagious disease, and in 
this way many outbreaks may occur without the origin of the infection 
being discovered. 

In the more pronounced forms of swine fever the symptoms which 
are shown by the sick animal will uot be very definite until the affection 
is fairly advanced. Dullness and diminished appetite, with hot skin 
and occasional shivering tits, with rise of internal temperature from the 
normal 103° to 105° or 100° F., are among the first signs of infection, 
and should always be taken as justifying a strong suspicion of the ex- 
istence of swine fever, espedialiy if the disease is known to be in the 
locality. 

It has been remaiked that pigs when suffering from swine fever in 
the early stage often seek to hide themselves beneath the litter on the 
floor of the stj* ; but this action is so common among swine that it 
would hardly be likely to attract any attention, and even when noticed 
it would not be looked upon as a symptom of any disease. There is, 
however, to the practiced eye a great difference between a healthy pig, 
which, in its desire for warmth, or quiet, or for some other reason, buries 
itself under a lot of litter, and one which performs the same act inobe- 



175 

dieuce to the instiuctivc oftoit of a sick aiiiinal to jrct out of the way 
of the light aucl its coiiipauioiis, and everything nuder the sun, and 
suffer in seclusion. Tlie liealthy pig when disturbed emerges from its 
rt'treat al( rt and ready for action. The sick one objects to move, and 
if compelled, crawls tVoni his lair, trembling and discontented. 

Sometimes tliere ai() signs of partial paralysis, and the pig moves in 
an unsteady manner trom side to side, Irequently losing the use of one 
or buth hind quarters, aiul dropi)ing to one side, or dragging both hind 
legs as it attempts to move forward. There is no loss of sensibility 
wilh the defective motion, as the animal if touched will indicate pain 
by a sharp cry. 

Diarrhea may occur early in the disease, after a short period of con- 
stipation ; and the evacuations are generally light in color at first, be- 
coming darker by and by, often from the mixture of effused blood. In 
severe cases the intestinal discharge consists almost entirely of blood, 
with masses of clot and loosened |)ieces of exuded lymph from the in- 
flamed and ulcerated mucous membrane of the digestive canal. 

A symptom which is considered to be characteristic of swine fever 
may sometimes be detected early in the disease. Eed patches or 
blotches a]ipear behind the ears, inside the arms, and under the bell^'. 
Professor Axe describes a distinct eru])tion in the form of red spots, 
from one to three lines in diameter, slightly raised above the surface, 
so that they may be felt by drawing the finger over the skin. The erup- 
tion is not always present, and often there are not more than half a dozen 
spots extending over a large surface; but in other cases they are very 
numerous. After two or tlirce days the spots subside, and are followed 
by a second, third, or even a fourth crop, and after their final disap- 
pearance the cuticle becomes ragged and scales off. 

Small water bladders (vesicles) appear on the surface of the red spots 
when the fever remains very high, and the tluid contained in them either 
escapes or becomes dried up, forming a gray crust on the surface. 

Discharges of thin fluid from the eyes and nose commonly takes place 
early in the course of the disease, and, as it advances, the discharge 
becomes thick and purulent, sticking about the eyelids and openings 
of the nostrils. Diarrhea is more constant as the disease goes on. The 
voided matter is offensive and often streaked with blood; prostration 
occurs and is soon followed by complete collapse, and the animal dies 
in a state of unconsciousness or in violent convulsions. Death may take 
jdace at various periods from the commencement of the affection, some- 
times after a few days' illness, while in other cases tie animal may linger 
for two or three weeks. 

In reference to the change of the color of the skin in marked cases of 
swine fever, it may be observed that there ma^^ be, independently of 
the raised spots which Professor Axe describes, a diffused redness, or 
regular i^atches of redness, or a purple tinge in different parts of the 
surface; but these signs are not to be expected in all or even in the 
majority of cases of the disease; and it is well known that redness of 
the skin is a symptom of some common diseases of swine. It arises, for 
example, from exposure to wet and cold ; contact with sea- water, or 
spray during a voyage, will also produce it; a journey in a railway 
truck which has been lime washed is another cause; consumption of 
wash with which salt liquor has been mixed is followed by severe, often 
fatal, inflanmiation of the mucous membrane of the digestive canal and 
sympathetic irritation of the skin; and the symptom has also been 
noticed in acute indigestion which has resulted from eating freely of 
mangolds. Redness of the skin, therefore, either in patches or gener- 



17G 

ally, cau not be acce[)ted as snfficieiit ovideuce of the existeuce of the 
swine fever. 

In certain instances tlie symptoms of swine fever may be so well de- 
fined during life that an opinion may be given promptly and withont 
much risk of error, but ni^^ler ordinary conditions the conclusion must 
be the result of the careful consideration of the history of the outbreak, 
or of the evidence which can be obtained by dissection of the organs of 
a diseased animal; and for this purpose it is better to kill a suspected 
pig than to take the carcass of one which has died some time before the 
commencement of the inquiry, and has probably undergone post-mortem 
changes which will render obscure the true morbid appearances. 

Experience has placed beyond all doubt the fact that swine fever 
when it once obtains a hold on a herd of swine does not spare them. 
It is true that a proportion, and it may be a considerable one, of the 
older animals particularly, will escape with a mild attack, and in some 
of these mild cases there will be no characteristic symptoms to attract 
attention. In fact, it will appear that animals have escaped the dis- 
ease ; but the critical observer will find some signs of the disease in the 
majority of the swine which have been exposed to infection. Cases 
which arc often reported of swine fever attacking two or three swine of a 
large herd and sparing the rest may safely be put down to the credit of 
any disease but swine fever. And the same thing may be said of those 
cases which are traced to the consumption of indigestible food, or the 
exposure of the animal to hardship or unsanitary conditions of exist- 
ence. 

Fostmortcm appearances in sicine fever. — Some of the changes which 
are affected in the organs of the body by the ravages of swine fever 
can only be appreciated by the pathologist ; others, and those most 
distinctive perhaps,, are patent to the ordinary observer; and on this 
point it is worth while to note the description which was given before 
the members of the Eoyal Agricultural Society in 18G5 by Dr. William 
Budd, of Clifton, who was the first scientist in this country to investi- 
gate the disease, which was at that time looked upon as a new one. 
Dr. Budd's attention was particularly attracted to the changes which 
Lad occurred in the digestive organs, which he called a series of ulcer- 
ations of peculiar character, variously distributed over the intestinal 
tract, from the stomach to the rectum inclusive. 

The first stage of the local affection appears to be the development 
(amid all the phenomena of acute inflammatory disturbance) in the sub- 
stance of the mucous membrauce and in the submucous tissue of an 
adventitious deposit (or cell growth) resembling in manj^ of its charac- 
teristics the well-known yellow matter of human typhoid. When Dr. 
Budd gave this description, the outgrowth from or deposits on the mu- 
cous membrane of the stomach and intestines were seen more frequently 
than they have been of late years; in fiict, in all well marked cases 
they were the prominent objects in the post mortem appearances — soft, 
spongy masses, sometimes in very severe cases stained a dark red by 
the blood, which was extravasated into the intestines, varying in size 
from that of a large pea to a walnut, circular or oval in shape; some- 
times several masses were joined together; but whether large or small, 
separate or confluent, the deposits, from their color in contrast with the 
membrane on which they were placed, were very striking objects. 

A very curious appearance was sometimes seen in the intestines of 
swine which had partially recovered from the fever and afterwards died 
from exhaustion, or were killed for the purpose of examination. The 
mucous membrane in these cases was spotted with the small masses of 



177 

deposit wliicli had lost the soft, spongy or fungoid character, and be- 
come dense and, so to speak, leathery looking, not unlike yellow leather 
buttons, marked with concentric rings, or, as Dr. Budd remarks, like 
slices of columba root.* 

The first simile will i)erhaps be more suggestive to the farmer than 
the latter, as slices of columba root are not familiar objects. The mu- 
cous membrane of the intestines, especially the large intestines, was 
often covered with ulcers, and the masses of deposit which have been 
referred to were generally found to be in connection with deep excava- 
tions, the result of the ulcerative process ; but in all cases the edges of 
the ulcers were elevated above the surface of the mucous membrane, 
and presented a soft fungoid character. 

In some cases the whole of the mucous membrane of the intestine 
was covered with a croupous or diphtheritic deposit of a dirty white 
color; and it was only after the deposit had been cleared away that 
patches of inflamed, and perhaps ulcerated, structure could be seen. 

In some instances tlie dipliiheritic deposit was so abundant as to fill 
the intestinal tube, and leave no canal for the passage of the feculent 
matter, and rupture of some part of the intestine was the natural re- 
sult of this blocking up of the passage. 

The next illustration is copied from a report on swine plague in the 
Keport of the Bureau of Animal Industry, Washington, United States 
(for 1885), and it may serve to indicate at the same time the character- 
istic appearances of the disease and the identity of the swine plague 
(hog (;holera) in the United States of America and the swine fever of 
this country. 

Besides the appearances which have been described as occurring in 
the stomach and intestines, especially in the large intesrine, there are 
nearly always observed patches of congestion in the lungs, with here 
and there condensation of the lung structure, which ])resent a ilesby 
character quite distinct from the healthy state. There are also changes, 
easily distinguished by the pathologist, in the liver, kidneys, spleen, 
lymphatic glands, and also in the cr^vities of the heart. In short, it 
may be aflirmed that the moibid changes in swine fever are so ])er- 
fectly well detined that no error in opinion can occui when all the evi- 
dence which a post mortem inspection aftbrds is in possession of the 
inquirer. 

In this description we are led to infer that the writer has before him 
genuine hog cholera. At the same time some of the features dwelt upon, 
such as the croupous and diphtheritic deposits or exudates in the large 
intestines, are more like those found in severe epizootics of swine 
plague. t 

There is another fact which proves that at least part of the swine 
fe\ er of England is the hog cholera of the American continent. This is 
presented by the investigations of E. Klein. In his report upon swine 



* These neoplasms wo have also encouutereil chiefly in adults. They mnsb be 
looked upou as results of a greater resistance on the partof tlie mucous membrane, 
such as we may expect in old animals. 

t A phigiie like hog cholera may ]ierhaps change its character under influences such 
as climate and locality, or under influences found in race, breed, etc., of animals. This 
may frequeutlj' account for modifications of diseases causfd by the same micro- 
organism. 

15612 H c 12 



178 

fever in the supplement to the Seventh Auimal -Eeport of the Local Gov- 
eniiueut Boanl for 1877 Dr. Kleiu gives a very good account of the 
pathological anatomy of this disease, together with some researches on 
The nature of the cause and the mode of infection. Though calling the 
disease pneumo-enteritis, his text, as well as the statements of Professor 
Brown, quoted above, show that the accompanying lung disease is no 
more severe than in hog cholera. The microbe which he described in 
this re[)ort is a large spore-bearing bacillus. The methods which he 
emi)loyed in his bacteriological work were those of the times, not con- 
sidered now as capable of giving any trustworthy information. Conse- 
quently, at a later date he regarded it as necessary to again go over the 
ground, and published his results in Yirchow's Archiv, XCV, 4C8, in 
IbStt. In this monograph he describes the inoculation disease in mice 
and rabbits very much as we have found it, laying particular emphasis 
u[)o;i the coagulation necrosis found in the liver. His cultures con- 
tained a motile bacillus from .002 to .003 millimeter in length. We may 
therefore conclude that a germ closely resembling or identical with the 
hog cholera bacillus is found in cases of swine fever, and that hog 
cholera actually exists in England. 

The history of the struggle with swine lever in Great Britain since 
1878 shows that it has been very severe. iSTumcrous orders have been 
issued, beginning with the contagious diseases aet in 1878, to restrict the 
extension of the disease, but all appear to have been without avail, since 
the malady was as widespread and as virulent in 1885 as ever before. 
This was without doubt due to the inefiicient and incomplete execution 
of the orders. By the order of December 17, 1878, the slaughter of 
swine affected with the disease was made compulsory, and compensa- 
tion was to be paid out of the local rates for all swine slaughtered by 
order of the local authorities. The order also provided that no swine 
should be moved out of a pig-sty or other jdace without a license, and 
then only for slaughter. After this order had gone into effect weekly 
returns were received from the inspectors of local authorities, which 
showed that in 1870 the disease had prevailed, at some time during the 
year, in forty-four counties in England, six in Wales, and three in Scot- 
laud. 

The continued spreading of the disease gave rise to the swine fever 
order of 1879. This contained provisions for the declaration of infected 
places and for the slaughter of healthy swine which had been herded 
with diseased ones, and also for regulating the exposure for sale of swine 
in fairs and markets. This order was only partly carried out, for out 
of 17,074 swine attacked 3,410 were allowed to die and 124 recovered. 
In 1882 the disease was more prevalent than in 1870. Slaughter of 
diseased and exposed animals was continued as before. Tlius of 14,703 
swine attacked 11,903 were slaughtered, 2,799 died and 18 recovere<l. 
An order of council was passed in July, 1882, providing for the decla- 



179 

ration of swine fever iulectecl areas by the privy council, and giving- 
power to local authorities in England and "Wales to prohibit or regulate 
the movement of swine into their districts from the district of any 
other local authority in Great Britain. The order also empowered 
local authorities in Scotland to prohibit or regulate the movement into 
their district of swine from the district of any other local authority in 
Scotland; it did not appear, however, that the local authorities availed 
themselves of these powers, excei)t in very lew cases. 

In 1884 the area of the disease rather increased, while the number at- 
tacked did not grow larger. Further orders of council were passed 
this year containing provisions relating to swine fever. The most im- 
l)ortant change made leferred to thcjirovision for slaughter of diseased 
swine, which was objected to by some local authorities a,s a costly and 
comparatively ineffectual measure. By an order passed in May the 
compulsory provision was revoked, and the slaughter of diseased swine, 
as well as those herded with them, was left to the discretion of the lo- 
cal authority. Another order of council, passed in July, 1SS4, pro- 
vided for the formation of a swine fever infected circle round an infected 
place in any district to which the order might be applied by the privy 
council at request of a local authority. The order was applied during 
the year to five counties and ten boroughs. 

In 1885 the disease grew to dangerous proportions, threatening the 
■ entire stock of pigs in the country. The extension was due to the pur- 
chase of swine at fairs and markets, and it was therefore deemed ex- 
pedient to impose restrictions on the sale of swine in all parts of Eng- 
land. Accordingly an order of council was passed i)rohibiting the ex- 
l^osure for sale of swine except for slaughter within three days, and then 
onl}" with the license of the local authority of the district in which the 
sale was to be held. Provision was also made for the exhibition of 
swiue at agricultural shows. 

This so-called markets and fairs order did a great deal of good, but, as 
it did not prohibit private sales, the disease even increased in some 
counties, owing to the unrestricted sale and movement of swine. 

"It was continued in operation until the end of November, and dur- 
ing its operation the centers of disease were so far advanced in number 
that it was dcen)ed expedient to have recourse to slaughter of diseased 
swine, an^l also of ihose which had been in the same pigsty or shed with 
diseased swine. With this view the swiue fever compulsory slaughter 
order was passed, and came into operation on the 1st of December. The 
order provided that local authorities should slaughter all swine that at 
any time in the month of December were afl\.'cte(i with swine fever, and 
all swine being or having been in contact, or in the sasne pig-sty or 
shed, with swiue affected with swine fever. 

'' Compensation was to bo i)aid to the extent of half the value of a dis- 
eased pig and the full value of a healthy pig, but the amount was not 
to exceed 4:0s. for a diseased and £4 ior a healthy pig. During the four 
weeks to the end of 1885, the efl'ects of the system of compulsory 



180 

slangbter were not altogether satisfactory. In fact, fresli outbreaks of 
su'ine fever continued to occur in the same districts, and even in tbe 
same premises, owing to tlie way in wliicli the order was carried into 
effect in regard to tbe slangbter of swine wbicb bad been exposed to 
infection. For example, if a lot of swine were in a sty wbicb was sepa- 
rated a few feet from tbe sty in wbicb disease existed, tbe animals were 
not slaugbtered, because tbey could not be said to be in contact, and 
tbey w^ere clearly not in tbe same sty, altbougb it migbt fairly be j^re- 
sumed tbat tbe swine so situated were exposed to risk of infection 
tbrougb tbe atmospbere, or by tbe agency of persons or tbings bv wbicb 
tbe virus of tbe disease could be conveyed to a considerable dis- 
tance. * * * 

" Slangbter of diseased and infected swine was adopted in some dis- 
tricts witb satisfactory promptitude. In otbers a number of animals 
were allowed to die before any action was taken. Tbe disease, after 
being stamped out in some districts by tbe energetic action of tbe au- 
tborities, was reintroduced from otber parts of tbe country wbere tbe 
law was administered in a perfunctory manner. In sbort, notbiug like a 
serious and decided effort was made to get rid of tbe affection, and as a 
natural consequence tbe good effects of restrictions were partial and 
temporary. 

"Imperfect cleansing and disinfection of premises may be reckoned 
among tbe causes wbicb have contributed to tbe continuance of swine 
fever, notwithstanding the operations of regulations which migbt have 
been expected to produce good results. Very frequently swine are 
ke])t in places which can not be cleansed and disinfected effectually, so 
as to make them safe for tbe next lot of pigs which will be brought in 
as soon as the place is declared free. Old, half rotten styes witb moldy 
floors can not be cleared of infection by .any known process. The only 
course in such cases is to remove tbe infection-saturated timber and soil 
and submit them to tbe action of fire; but no power is vested in the 
authorities to do this necessary work, and tbe only exiiedieut wbicb 
tbey can employ is tbat of refusing to declare tbe infected premises free 
until tbe necessary alterations and improvements are comjjleted. In 
thin somewhat roundabout way tbey may attain the object — that of 
keeping out fresh swine to become victims to the disease, but this kind 
of pressure can only be applied under certain circumstances. 

"Free niovement of infected and of actually, although not observably, 
diseased swine, and their exposure in fairs and markets, has all along 
been a fruitful cause of the spreading of swine fever. Many inquiries 
have been made with tbe view of tracing the origin of different out 
breaks, and tbe conclusion has generally been that they were due to 
introduction of swine recently i)urcbased at public sides. 

" Under the system, which has obtained for years, of slaughtering dis- 
eased swine, and allowing the apparently healthy to live, tbe extinction 
of tbe disease could not possibly be secured. And it is only in the com- 
mon course of tbings tbat tbe malady has gradually extended all over 
the country from the sale and movcnient of diseased and infected swine 
which often showed no signs of disease, and would be passed as free 
from swine fever by any one but an expert who is familiar witb every 
phase of tbe maladj'. * * * 

"In reference to the measures which should be adopted for tbe ex- 
tinction of swine fever in tbis kingdom, it is not necessary to enter into 
details. On three occasions in the last twenty years tbe stamping-out 
system was successfully applied to cattle plague. Exactly tbe same 



181 

means wonUl certainly succeed in ridding us of swine plague, and there 
is no ground for the ex-pectation that any less severe measures of re- 
pression would be effective. It is, however, an essential condition of 
success that the action taken should be uuiform and general in applica- 
tion. But it is impossible to suggest any means of securing the neces- 
sary uniformity -while the execution of the law is in the hands of some 
hundreds of local authorities who entertain different views as to the 
necessity for attempting to get rid of the disease by legislative meas- 
ures, and are not agreed as to the proper means of effecting the object." 

SWEDEN AND DENMAEK. 

Ill the fall of 1887 a disease closely resembling hog cholera appeared 
in Sweden among swine, which rapidly spread from i)laco to i)lace, 
showing itself very fatal and causing alarm and consternation among 
the agricultural population. The disease invaded the territory of Den- 
mark, where stringent measures were adopted to prevent its further 
spread. The following commuuication, received by the Denartmeut of 
State from our consul at Copenhagen, andkindly forwarded, may serve 
to illustrate the measures employed by the authorities iu checking the 
epizootic. After giving briefly the symptoms of the disease, and tlio 
lesions caused thereby, Mr. TI. B. Byder continues as follows: 

The very prompt and stringent measures taken by the Banish Gov- 
ernment, it is to be hoped, will be the means of localizing as well as of 
effectually stani])ing out tliis malignant p.est. For exami)le, circulars 
have been sent from the home department to all the sheriffs through- 
out the kingdoni, instructing them to nmke publicly known that all 
persons wiio within the last two months may iia\e purchased hogs or 
young pigs trom Copenhagen, or iu its vicinity, should immediately give 
notice thereof, so that their entire herds might be submitted to veter- 
inary inspection. Furthermore, an ordinance has been issued strictly 
})rohibiting all transport of live hogs or young i)igs from one district to 
the other , and that no reniovi^l of the animals shall be made from their 
present dwellings, excepting by special permission for the puri)ose of 
immediate slaughter; and, lastly, power has been given to all the jiolice 
authorities, on any suspicion of disease, to order the immediate slaugh- 
ter of the animals, and a j)ost-mortcm examination of the carcass to be 
made by the veterinary otticials; and on the appearance of the disease 
in any locality under their jurisdiction to order the immediate slaughter 
of a part or the entire herd as may be deemed necessary. 

It is thus to be hoped that by these nieasures further spread of the 
disease may be arrested. It is, however, much to be feared that, in 
addition to the looses entailed upon the kingdom in the destruction of 
animals in the course of the disease, the sorely tried farmers in these 
days of agricultural depression will also be sulijeted to material loss in 
a diminished sale to foreign countries of their swine products. An 
order has already been issued by the German federal council prohibit- 
ing all importation into the German Empire of swine, pork, and sau- 
sages from Sweden, Norway, and Denmark, which will be most seriously 
felt by the agricultural interests, as tiie exports of live hogs and young 
pigs are almost entirely directed to Germany, whilst the exports of pork 



182 



nnd bams arc maiuly forwarded to Great Britain, as will be seen by the 
t'ollowing table, namely: 



Of I'.vo Logs ami pigs to — 

Goiruaiiy 

Xorway 

reat Britain 

nolland 

Of pork aud Lams to- 
Great Britaiu 

Germany... 

Sweden 

iKorway 



Avcrajro 
1881-3885. 



1S85. 



TTead. 

27G, ICC I 
G, 8ti I 
2,893 ' 
1,213 

rounds. 

12, O.'O, 000 
2, 030, 000 
3,070,(00 
1, COO, 00 J 



Head. 
192,273 
4,704 

123 

Pounds. 

20, 240, 000 

7, 180, 030 

0,030,000 

700, ceo 



From the lbregoiii<2^ figures full evidence is alibrded that wliilst tbc ex- 
ports of live stock have met with considerable decline in tiie latter years 
a great increase has taken idace in the exports of sv.'ine prodncts, due 
to the large nnmber of slanghtering and salting establishments which 
have been erected in this conntry for the development of the pork, ba- 
con, aud ham trade with England; and thus the loss to the agricultural 
interests, it is to be hoped, will not be quite so severely felt as would 
have been the case in former years under similar unfortunate conditions, 
and it is scarcely to be feared that England will likewise place obstacles 
ill the way of the free imports of the i)roducts into her ports ; for inas- 
much as the imports of swine into Great liritain from this conntry have 
for some time only been admitted in slaughtered condition, and set- 
ting apart the facts that swine in mature stage for slaughter are farless 
exposed to this disease thanyoung])igs, there will be found at the same 
time, under the close inspection which has been introduced throughout 
the Kingdom, and the energetic steps taken by the authorities in all 
cases of suspicion, an almost certain probability that no pork from a 
diseased animal can possibly l)e exported. The sale of swine products 
forborne consumption i»lays likewise a very important part; audit is 
here again to bo feared that restricted sales will be t-ensibly felt until 
the temporary scare iu i)artaking of swine flesli lias had time to sub- 
side. 

lu order tiiat the energeti<; measures taken by the Government for 
the stamping oat of the plague may be crowned with fidl success it will 
be necessary tb^it theagricuUurists should give at the same time a loyal 
support to the issued instructions' and work baud in baud witb the au- 
thorities. He who may delay in reporting or may attempt to conceal 
any disease or susi)icioi) of disease that may show itself at bis place 
will simply be committing a crime against the class to which he be- 
longs, and honesty in this as well asin other cases will be found the 
best policy; for whereas be who rcjwrts the breaking out of disease 
amongst his stock will receive two thirds of the valueof the slaughtered 
diseased animals, and full compensation forthe slaughtered sound ones, 
the dishonest party will incur not only risk of confiscation of the dis- 
eased meat offered' by him for sale, bu't*will also render himself liable 
to heavy fines. The closing of Germany to the importation of these 
products undoubtedly can not fail to entail severe loss upon the agri- 
cultural classes ; but if success can only attend the stringent measures 



183 

adopted for preventing tbefurtlier spread of tliedisease it must be hoped 
the prohibition will be of short duration, and that agricultural interests 
will soon recover from the blow. But should the devastating plague, 
on the other hand, spread over the whole Kingdom it wdl be nothing- 
short of a national calamity, the destructive effects of which will long 
be felt, as will easily be understood from the following table of theiium- 
ber of hogs and young pigs to be found in the Kingdom under census 
of 1S81, vrz: 



i nogs. 


Tonng pigs. 

Head. 
392, 884 
334, 707 


■ 1 

! Bead. 

In the isliuuls 285,317 

In Jutland i 242, 100 




Total 527,417 


7-27, 591 



Great responsibility will thus rest not only upon the veterinary and 
])olice authorities but also upon the agriculturists in devoting all possi- 
ble energy in their mutual exertions to prevent the further si)read of 
this dreaded evil. 

The disease is supposed to have been introduced into Sweden by dis- 
eased boars, imported from England for breeding purposes. Thence it 
was carried to Denmarl^,* in which country it first appeared on the 
dumping grounds near Copenhagen, on vthicli numbers of swill fed pigs 
were kept. 

Chiefly young pigs up to the age of four months were attacked, the 
period of incubation lasting from five to twenty days. The infected 
animals refused food and were at first constipated. Later on diarrhea 
set in, characterized by the discharge of yeliow i)utrid masses, frequently 
mixed with blood. The temperature often rose to 105^-107. 5° F. The 
animals were indifferent to surroundings. Tail and head drooping. 
Conjunctiva reddened, frequently glued together with dried up mucus. 
Respiration in many cases quickened and labored. Occasionally a muco- 
purulent discharge from the nose. Not infrequently reddening in jiatches 
was observed on the ears, snout, abdomen, about the anus, and inner 
side of thighs. The animals became very weak ; posterior part of body 
swayed in moving about. They concealed themselves in the bedding 
and finally were unabl.:- to rise. Death followed insensibility and con. 
vulsions. 

A characteristic sign of this plague were dii)htherilic changes on the 
ai)ex, sides, and under surface of the tongue, as well as on the mucous- 
membrane of the cheeks, hard and soft palate, and the tonsils. On these 
l)arts grayish white or yellowish opaque patches appeared, which were 
sharply defined and were converted later into ulcers by removal of the 
slough. 

In one herd the teats of several sows were affected with dark gray, 
sloughing sores, with inflammation of the udders. These were infected 



^Scliiitz: Die Schweinepest in Dnnemark, Arch. f. wins. n. prakt. 
1888, p. :?7a. 



ThicrIidlki(:H}f,Xiy, 



184 

from the diplitberitic sores in tbe moiitlis of the sucliiug pigs. lu Deu- 
mark tbe disease was first recognized in tbis way. Tbe acute disease 
lasted from five to eigbt days, but sometimes dcatb occurred sooner 
tban tbis. 

Tbe disease appeared in Denmark in SepLember. In December tbe 
plague took on a more cbronic character and became less infectious. 
Tbe iufected animals frequently sbowed no indications of disease, only 
tbey were smaller and tbiuuer tbauotbers of tbe same age. TbercAvas 
occasionally congbing and diarrhea. Some recovered, otbers perished 
by a gradual wasting- away. Tbe postmortem ai)pearances were very 
characteristic. Tbe large intestine was attacked in every animal, and 
in acute cases tbe small intestine and stomach likewise were reddened 
and swollen, and Ibe surface in part covered with a thin layerof a gray- 
ish white or grayish yellow soft mass, which consisted of fibrin. Tbis 
same layer was very tliick in the large intestine, easily lifted away in 
toto in sonic places 5 in others the attachment was firmer (diphtber 
itic). In other acute cases there was simply reddening and swell- 
ing of the mucosa of stomach and small intestine, and diphtberitic 
changes in the large intestine, the fibrinous exudate being absent. 
Moreover, the follicles, Peyer's patches, and mesenteric glands were al- 
ways tumefied. 

The seat of the diphtheritic process was the whole large intestine, 
more especially the ca.'cum. The follicles and Peyer's patches were 
nearly always affected. Tbe ulcers appeared when tbe slough had come 
away. In tbe place of tbe follicles button like sloughs were formed, 
which gradually invaded tbe whole thickness of tbe wall, spread later- 
ally, and ran together into larger jiatches. Tbe wall thus converted 
into a cheesy maes was frequently one-fifth to two-filths inch tbick, on 
the surface irregular, colored yello\v, brown, or green. Hemorrhage, 
duo to tbe ulceration, was observed in one case. 

In many animals tbe lungs were healthy. In some a mucopurulent 
catarih of tbe broncbi was ])resent, which caused atelectasis in one or 
more places with young and weak animals. Usually tbe ventral and 
anterior lobes were affected. In the diseased lobes homogeneous, 
cheesy masses appeared later, sometimes as large as walnuts. These 
masses led subsequently to iuflammation and adhesion of tbe pleura to 
chest-wall, pericardium, etc. Tbe spleen was not changed as a rule. 
In a few cases only it was somewhat enlarged, soft, dark red. 

When we compare tbeselesions with those found in our country, we ob- 
serve the absence of hemorrhagic lesions and enlargement of the spleen, 
and more marked exudative and diphtheritic changes iifthe large intes- 
tine. In numerous sections of ulcerative changes we have not observed 
any relation between these and the follicles. The lung lesions corre- 
spond closely. Whether they arc due to the disease or not must be left 
undecided. We have frequently seen caseous changes in tbe lungs 
of animals free from infection, and they are, perhaps, due to collapse. 



185 

broncbopneumonia. and subscqneut interference of tbe circulation, 
rather than to the direct action of bacteria. 

The specific bacteria which are the cause of the swine disease are 
described briefly by Selander,* and according- to his description they 
closely resemble hog cholera bacteria in form, motility, growth in gela- 
tine, and appearance in tissue. Their growth on potato is said to re- 
semble that of the bacilli of typhoid fever in man, and thus to differ 
from that of hog cholera bacilli. Their effect on the lower animals cor- 
respond also, although the descriptions are too brief for careful com- 
parison. There is no mention of the coagulation necrosis found con- 
stantly in the liver of rabbits inoculated with American hog cholera. 

In the beginning of the present year (188S). Dr. John Lundgren, pro- 
fessor of veterinary medicine in the University of Stoclvholm, was sent 
by the Swedish Government to study swin*^. diseases in this country. 
He spent several weeks in the laboratory of the Bureau studying the 
bacilli of hog cholera. A culture of the swine pest bacilli from the 
Swedish epizootic was at that time subjected to a careful examination. 

In gelatine, the swine pest germs grow very much like hog cholera 
bacilli. On the surface of the gelatine the growth is very thin,triu8lu- 
cent, of a pearly luster, and spreads more -rapidly than the hog cholera 
growth. On agar-agar the growth is more abundant and more rapid. 
Beef infusion, with or without peptone, is converted into a very turbid 
liquid within twenty-four hours at 95<^ F., while hog cholera cultures are 
barely opalescent at that time, and remain so. Two mice were inocu- 
lated from an agar agar culture of the Swedish gerai under the skin of 
the back. Both were slightly ill next day. On the second day one 
was found dead. The cultures from it remained st( rile. It probably 
died from some other cause. The second mouse remained well. On a 
rabbit the effect was equally negative. No rabbit survives inoculation 
with hog cholera bacteria. 

The effect of both germs on pigs was next tried. Two Erlenmeyer 
flasks, containing each about SOOcubic centimeters (two-fifths of a pint) of 
sterile bouillon, were inoculated, one with the American, the other with 
the Swedish germ, and placed in the thermostat at 05° F. On the follow- 
ing day both flasks were clouded ; the Swedish culture was covered by 
an iridescent, very thin membrane. A comparative microscopic exami- 
nation showed the Swedish bacteria to be nearly twice as large as the 
American; their movement was far less active than that of the latter. 

On the same day two pigs, starved for about twenty four hours, were 
fed with these cultures by drenching, /, e., the liquid was poured into 
the mouth, so that none was lost. The pig fed with the Swedish culture 
showed no signs of disease at any time after. The other pig on the 
fourth day had a very liquid diarrhea, and was found dead the next 
morning. On examination the spleen was found gorged with blood, 
but only slightly enlarged. Mesenteric glands enlarged and reddened. 

* Centralblattf. Ballcriohxjie, etc., 1838— i, 3Ga. 



186 

Stoniacli aud ileum intensely inflamed (enteritis); grayish masses (diph- 
theritic) attached in patches. The ileum was invagiiiated and ])rojected 
for L*^ inches into tlie ciecum; mucosa of this portion necrosed; walla 
inhltrated, thickened, and ecchymosed. In eim^uin the mucosa was cov- 
ered by a very thin slough. In the colon the membrane was deeply 
reddened, covered by a catarrhal exudate, and dotted with numerous 
very minute ulcers. Heart and lungs normal. Koll cultures in gela- 
tine as well as liquid cultures from the spleen contained only hog cholera, 
bacteria. The invagination was* very likely the result of the violent 
inflammation. 

These comparative experiments show that the two germs, though 
very much alike in appearance, were quite different with reference to 
their pathogenic effect. Professor Lundgren was inclined to the opin- 
ion that he had taken the wrong culture on leaving his native country. 
It may also not be improbable that this was the true germ attenuated 
on the way hither. As no communication has been received from liiiu 
since his visit here, the question must remain an open one. 

FEANCE. 

During the summer of 18S7 a disease was introduced into the vicinity 
or Marseilles by swine from Africa, which devdoped into an epizootic 
of a very fatal character. It caused great losses in the south of France, 
and at the time scientific men uere sent from Paris by the Government 
to investigate the cause aud suggest a remedy, if possible. According 
to Rietsch, Jobert, and Martiuaud* the disease is chiefly restricted to 
the intestinal tract, lasting from ten to twelve days after the first symp 
toms have appeared. Occasionally it may last but three or four days, 
or be prolcnged to several weeks, but it is quite invariably fatal. Some- 
times there is diarrhea, sometimes constipation ; the fever is not con 
stant, the cough very rarely heard. The hind limbs are weak, the walk 
tottering. Appetite often persists to the end. The skin may become 
reddened in spots, especially on the limbs and ears. Pigs over a year 
old are much less susceptible. 

At the autopsy the lungs, liver, kidneys, and spleen are usually found 
unchanged, and the disease limited to the digestive tract. The stomach 
and the small intestine near the valve are ulcerated. Ulcers are presi^it 
in the large intestine on the valve, in the ciecum and colon. They may 
measure 3 to 4 inches in diameter. In animals affected with a chronic 
form of the disease, there may be ulcers on the inferior surface of the 
tongue and on the inner aspect of the lips. The internal organs are 
free from bacteria. But from the contents of the intestine and the ulcers 
a motile bacillus was obtained. Mice are killed in ten days after sub 
cutaneous inoculation wich cultures of this organism. Of ten aduit. 
mice fed with cultures two died in fifteen days. Of ten young mice all 
Compt rend. Acad, /Sciences, Jauuary 2ti, 1888. 



187 

(lied wheu fed, the first in thirty hours, the others in fifteen to twenty- 
three days. Eabbits are but slightly susceptible. A young guinea- 
pig, fed with cultures, died twenty-two days later. The intestine showed 
characteristic ulcers. 

Dr. Rietscli very kindly sent to the Bureau a culture of the germ 
which he found. It was compared with the American hog cholera germ 
and the following characters determined: 

The motile bacilli of the same form as hog cholera bacilli, but larger, 
grow far more abundantly and rapidly in beef infusion. A thin mem- 
brane and a copious deposit are produced iu a few days, and the liquid 
becomes very turbid. On gelatine the colonies do not differ appreciably 
from those of hog cholera. The surface colonies s[)rcad iu thin irides- 
cent patches from 2 to 5 millimeters in diameter. In tube cultures the 
isolated deep colonies grow to about one-third of a millimeter iu diameter. 
On the surface the growth is rapid and spreads over the greater part of 
that which is available. The patch produced is whitish, uniform in 
thickness, very irregular in outline, inclosing round spaces of uncovered 
gelatine. In the bottom of the tube a few air-bubbles appear. On po- 
tato the growth forms a glistening, pale-yellow patch at the ordinary 
temperature. 

They thus resemble the Swedish germs very closely, difiering by so 
much from hog cholera bacilli. A rabbit and two mice inoculated with 
the Marseilles germ remained well. Equally so a pig fed with 400 cubic 
centimeters (four-fifths of a pint) of a beef infusion peptone culture. 

So far as our examination of the Swedish and Marseilles cultures 
have gone, they have shown them identi(;al both as regards their posi 
tive and negative characters. They differ from hog cholera bacteria 
enough to constitute at least a variety. But the iuvestigations of 
French savants of this Marseilles epizootic differ somewhat as to the 
cause. 

Cornil and Chantemesse* described a disease discovered aniong swine 
in the vicinity of Paris, which they consider identical with the German 
SchiccincseKclie and our swine plague. Subsequent experimentst to 
determine the biological properties of the bacteria causing the disease 
show that they are not dealing with the true swine plague germ (cer 
tainly not as we have observed it in this country), but with one resem- 
bling more nearly hog cholera. Their researches concerning vaccina 
tion are reported to have been successful on rabbits and guinea pigs, 
but since that time nothing has been published concerning experiments 
on pigs. 

While Kietsch and Jobert| come to the conclusion that the Mar- 
seilles disease resembles hog cholera closely, Cornil and Chantemesse 
regard it identical with swine plague, although the germ they describe 

* Covipt. rend. Acad. Sciences, 1S87, CV, p. 1281. 
\Compt. rend. Acad. Sciences, 1888, CVI, p. (;i2. 

t\. c, p. Km. 



188 

is not identical wiili the swine plague germ as studied in Gei many and 
in the United States.* 

It is interesting- in this connection to trace the march of infection in 
the soutb of France as reported to the French Academy by Fonquet as 
an excellent illustration of the ways by which infectious diseases may be 
scattered broadcast o>er a country: 

"The disease did not, as was supposed, appear in Marseilles toward 
the end of June, but in the month of April, and I have been able to locate 
three entirely distinct centers of the outbreak due to tlie same cause — 
the introduction of African swine. These three centers are : The village 
of Caillols, midway between Aubagne and Marseilles ; the village of 
St. Marthe, G'^'". northeast of Marseilles, and the herds of the Mediter- 
ranean distilleries. 

(I) From the 10th to the 15th of April, a breeder of Caillols received 
a drove of black swine from the province of Oran (Algiers). From the 
lirst week some cases of paeumonia| showed themselves among the last 
animals; the disease gained rajiidly, causing many deaths. The surviv- 
ors v/ere sold on the 1th of May following. 

On the 8th of June the same piggeries were restocked, partly with 
African and partly with Russian swine. Towards the end of the month 
there were cases of pneumonia. The Russian swine resisted less than 
the others. August IG the piggery was again emptied. Finally during 
September the third attempt was made, exclusively with African swine. 
This also i)roveda failure. The survivors were sold in October. 

During this time the disease reached the neighboring piggeries stocked 
with a mixed Marseilles breed. The breeders of Caillols, alarmed by 
the ravages of an ei)izootic the nature and cause of which they dul not 
know, decided to sell out at any price. The neighboring localities, St. 
Marcel, St. Loup, San Joan dii Desert, etc., were successively infected. 
Infection v\'as spread by the sales and exchanges of sick and suspected 
animals, by means of trans])ortation (carts often used in common by sev- 
eral establishments soiled by the dejections of the sick and afterwards 
used to transport healthy animals and their feed), and also by the lat- 
eral canal of Hu^■eaune, which receives at certain points running water 
coming from the grounds on which the piggeries are located. 

At the beginning of September all the valley of Huveanne, from Au- 
bagne as far as Marseilles, was infected. Diseased ])igs from this re- 
gion we meet again in the market of Aubagne, at the fair of September 
21, and which became later one of the most active agents in spreading 
the disease in the departments. 

(L*) Toward flic middle of the month of August the disease appeared 
in a piggery in St. Marthe, stocked exclusively wMth African swine. 
These animals came directly from Oran without coming in contact with 
any other of their species. Several days later one of the largest breeU- 
ers in that vicinity, who for three months had not brought a single pig 
to his establishment, and whose piggery was at least GOO feet away from 
the preceding one, sustained a considerable loss, especially among the 
pigs of 130 to 175 pounds. 

* lu a locont review of tlie ie}inrts of the Burean of Animiil Iiulnstry by Dnclanx 
(AiDinh'S dc V fnstitiit Pasieur, July, 1888), the reviewer regards this disease as iden- 
tical with hog cholera, and states that Coriiil and Chanteniessc had at first overlooked 
the molilitii of the r/enn thev were stndviug. 

1 1 c. p. G7U. 

t The writer calls the disease infections pneumonia for want of a l)etter term, 
although Rietsch distinctly states the intestinal nature of the malady. Fouquc was 
no doubt led astray hy the early, misleading notices of Cornil and Chantemesse. 



189 

(3) Filially, on the 2oth of June, sick pi.i>s came from Oran to the pig- 
geries of the Mediterranean distilleries. There were very soon a num- 
ber of victims of [)neumonia, not only in the distilleries but also in the 
neighborhood, where there ^Yere from 4,000 to 5,001) in a comparatively 
small territory. A great many of the sick died ; the others were quickly 
sent to ditiereut cities to be delivered to the butchers. I have traced 
the history of six sows which were sold from the midst of infection to 
Estaque; thence they passed through the commune Rove and arrived 
in August at Gignac, where they introduced the disease. By an odd 
coincidence some sick pigs from the same locality were taken to the fair 
at Aubagne and bought by a breeder of Gignac. 

The fair at Aubagne, on September 21, marked the most important 
phase in the progress of contagious pneumonia. During the first fort- 
night in October there was a veritable ex[)losion of the disease, which, 
up to this time, had been scarcely known. 

The importation of the disease by aniuials bought at the fair of Au- 
bagne can be traced with the great st precision in the suburbs south 
and north of Marseilles, also as far as Gardanne, in the communes of 
Septemes, Vitrolles, Pennes, etc., to Gignac, as mentioned above, even 
into the neighboring dci)artments, which continued with the others to 
receive consignments of Marseilles swine. It is also necessary to men 
tion Puget, Ville et Grasse, among the localities infected. 

In the beginning of December 153 swine were shipped from Mar- 
seilles to Nice; nearly all died in a few days. From that time cases 
ai)peared among the native pigs. 

Un December 22 another lot of 133 pigs were shipped; 33 were des- 
tined for Nice and 100 for Italy. These last were sold on the 24th, in the 
market of Vintimille; nearly all died very soon. 

For several years Marseilles annually exported to Spain, and es])e 
cially to Barcelona, a great number of pigs. Contagious jjuenmonia 
had been causing losses there for several months, even, it is said, at 
Majorka, in the Balearic Island^-. The Spanish breeders, believing the 
outbreak of the disease with them was attributable to the importation 
of French ]:>ork, obtained from the authorities the permission to imi^oso 
a quarantine of six days, at Port Bouc, on swine from Marseilles, to be- 
gin on the 1st of the following February. This measure has not been 
enforced up to the present day. 

From what has preceded I believe 1 can conclude that the epizootic 
of contagious pneumonia which has raged during the year 1887 in the 
interior of France, and which at this time continues its ravages there, 
is of African origin. It has been introduced by Algerian swine which 
came from the province of Oran. This disease has made 20,000 victims 
in several mouths in the province of Bouchesdu Phone. 

Pigs, and especially those from three to nine months old, areoftcnest 
attacked; larger pigs appear less susceptible. The Marseilles breed, 
the English (Yorkshire and Berksliire), and the Kussian swine are more 
susceptible than the African swine. 

T\A o months ago about 50 pigs two to three months old, coming from 
Cazeres and Le Fousseret, in the arrondissementof Muret, were used to 
stock a farm in Gignac. These pigs, placed in the pens which had con 
tained sick ones, and which had only been very imperfectly disinfected, 
remained in good health, while more than a hundred cases of conta- 
gions [)neumouia appeared around them in the same piggery. After- 
wards more than 2,000 Gascon swine were imported by the single com- 
mune of Gignac. Up to the present time the disease has not re-a])peared. 
Are we here confronted bj a new example of natural immunity com- 



190 

panible to that noticed long ago by Cbauveau in Algerian sheep in 
regard to anthrax ! " 

Taking into consideration what we know now of these epizootics and 
enzootics of swine diseases in foreign conn tries, we are forced to the 
conclnsion that the disease in Sweden, Denmark, and France is closely 
related to if not identical with hog cholera as it is found in our own 
country, while the minor differences in the disease as manifested in 
these epizootics, and in the germs producing it, can be explained on 
the principle of the variability of disease germs, a principle in favor of 
which much evidence has already been obtained in recent bacteriologi- 
cal researches. 



DESCRIPTION OF PLATES. 



Plate I : 

Casciiiii of a pig aftecte.ci with bog cholera laid open to sliow the ulcers of tho 
laucous luombrano. Th(5 ileo-ciccal valve is Dear the center of the page, and 
the small intestine, with tho cut end tied, is above. The smallest ulcers have 
slonghsofa uniformly yellowish color; the larger ones have zones of differ- 
ent color, while the largest are brown or blackish. It will be seen from the 
plate that the slongh or new growth in most ulcers projects slightly like a 
small flat button. 

Plate II; 

Caicum of a i)ig fed with viscera from a case of hog cholera, slit open to show 
the mucous membrane thickened and quite uniformly necrosed, with isolated 
deeper ulcerations. The ileo-crecal valve is very much thickened, its mucous 
membrane ccchymosed and ulcerated. The lymphatic glands of the meso- 
colon and those in tho angle formed by the entrance of the ileum into the 
csecum are purplish, with cortex engorged with extravasated blood. They 
illustrate tho condition of the lymphatics of both thorax and abdomen in 
the acute hemorrhagic form of the disease. 

Plate III: 

Caecum of a pig inoculated with blood from a case of hog cholera. The entire 
mucous membrane is necrosed. In the upper portion of tho figure about the 
valve there are groups of minute pigment spots. The valve is open to show 
tho intact mucosa of the ileum. This figure also serves to illustrate the con- 
dition of the mucous membrane of ctecum and colon in ]>ig8 fed with cultures 
of hog cholera l)acilli. 

Plate IV: 

CcBcum of a pig, showing round and elongated ( avities on and around the ileo- 
cEecal valve. These are ulcers from which the slough dropped away during 
removal. The base of the ulcers is formed by the muscular tissue of the in- 
testinal wall. Tbe ulcers appear as if the mucosa had been punched out with 
a sharp instrument. The edge of tho ulcers in the u[)per portion of the colon 
with the slough still adherent. The lungs in this animal were normal, if we 
except a few collapsed areas from one-half to tbreo-fourths inch across. 

Plate V: 

Ulcers in the lower portion of the small intestine (ileum); not very frequent. 
Note the large, deep ones with puckered, ragged border, and the very small 
ones with a thin superficial slough, stained with bile. 

Plate VI: 

Kidney from pig No. 7 (see p. 41), showing tho hemorrhiigic coiulition of cortex 
and engorged glomeruli. In this animal the disease was marked by the 
hemorrhagic condition of other organs. 

191 



192 

Plate VII: 

Right lung from a caso of hog cholera. The luDg tissue is nowhere iufiltrated 
or hepatized, hut studded with hemorrhagic sx^ots which are found iu the 
parenchyma as well as under the pleura. This animal, placed in an infected 
pen, died on the twenty-second day of exposure. There were hemorrhages iu 
the subcutaneous connective tissue ; lymphatics in general hemorrhagic. 
Petechia) iu stomach and large intestine. In the crecum and on the valve a 
few ulcers with hemorrhagic base. 

Plate VIII: 

Heart with subepicardial hemorrhages especially numerous on left auricle. 

Plate IX: 

Fig. 1. Collapse of various groups of lobules in the pr-ucipal lobe of a pig's lung. 
Frequently found in young pigs which have died of hog cholera, in those af- 
fected with lung worms, and in a small percentage of those slaughtered dur- 
ing health. 
Fig. 2. Broncho-pneumonia aifecting animals under various conditions and not 
infrequently fouud iu animals which have succumbed to hog cholera. (See j). 
54). The air cells and smallest air tubes arc shown distended with a yellow- 
ish material which is of a dry, caseous consistency, and may be teased out in 
the form of minute branching cylinders. 

Plate X: 

Fig. 1. From a cover-glass preparation of the spleen of a pig which died of hog 
cholera. Stained in an aqueous solution of methyl violet and mounted iu 
balsam. Outlined with a camera lucida, using a -j^ homog. immersion (Zeiss), 
ocular 2 (x 800) : a, distorted red blood corpuscle ; h, bacilli iu pairs. 
Fig. 2. Section from the enlarged and cougested spleeu of pig No. 94 (see Secoud 
Annual Report Bureau of Animal Industry, p. 193), which died very suddenly 
with extensive hemorrhagic lesions of A^arious organs. Spleeu hardened iu 
alcohol two hours after death ; stained iu aniline water methyl violet and 
decolorized in 1 per cent, acetic acid ; mouuted in xylol balsam ; outlined as 
in Fig. 1. Note the large group of bacilU occupying the capillary meshes of 
the siileen pulp, all extra-cellular. 

Plate XI : 

Illustrative of the growth of hog-cholera bacilli on gelatine. 
Fig. 1. Various colonies from gelatine plates : a, embedded in the gelatine layer 
(deep colony), usually spherical or egg-shaped; ?>, flattened colony growing 
on the surface of the gelatine layer; c, c', c", growing betweeu the layer of 
gelatine and the glass plate as very thin films; the knobs on c', c" repre- 
sent the part of the growth in the gelatine layer. 
Fig. 2 represents both deep {a) and surface colonics (h) growing iu a gelatine 
layer coating the inner surface of a test tube. A tube of gelatine was inocu- 
lated by stirring up in it, while liquid, a minute fragment of spleeu tissue 
from a case of hog cholera (No. 464, p. 51), transferriug a drop from this to a 
second tube, and then rolling out the latter in ice water. Culture seven days 
old. The zones on the surface colonies are very liiiely due to changes of tem- 
perature in the laboratory, alternately retarding and augmenting the growth. 
This mode of growth is by no means common. 
Figs. 3, 4, .'> represent the growth of hog cholera bacilli iu tubes of nutrient gela- 
tine, showiug the isolated colonies iu the depth of the gelatiue and the con- 
fluent growth on the surface. Fig. 3 represents a culture three days old 
(epizootic near Washington City, 18S5), inoculated from the spleeu of a pig. 
-Fig 4, fourteen days old, inoculated from a culture which was prepared di- 
rectly from the spleen of a pig iu Illinois, 1886. Fig. 5, inoculated from the 
blood of a rabbit which died from inoculation with bacilli from Illinois cult- 
ure ; ten days old. The difference in growth observed may be due to a 
greater or less alkalinity of the culture medium or to a slight physiological 
difference in the bacilli themselves. 



193 

Plate XII : 

Fig. 1. Jgar agar culture of hog cholera bacilli in thermostat, four days old. 

Fig. 2. Potato culture under a bell glass, twelve days old. 

Fig. 3. Potato culture in a test tube containing an abundance of moisture. The 
plug was made impervious with sterile paraffine. The growth is whitish, 
very glistening. The difference in color between Fig. 2 and Fig. 3 is caused 
by the different conditions of moisture. 
Plate XIII: 

Fig. 1. Coagulation necrosis in the liver of arabbit which died six days after in- 
oculation. The small, yellowish spots are groups of acini completely ne- 
crosed. The larger patch to the left shows the necrosis in the form of a net- 
work. 

Fig. 2. Liver of a rabbit inoculated with one thirty-second cubic ceutimeter (by 
dilution) of a beef infusion peptone culture one day old. Dead on the seventh 
day. The coagulation necrosis on the left is more ditfuse. On the right are 
cysts of coccidium oviforme. 

Fig. 3. Enlarged spleen from the same rabbit (natural size). Weight of rabbit, 
1| pounds. The spleen of this rabbit was but moderately enlarged as com- 
pared with the spleens of most rabbits which succumb to hog cholera. 

Fig. 4. Spleen from a healthy rabbit weighing 2| pounds (t. e., one and a half 
times the weight of the diseased rabbit. 
Plates XIV, XV, XVI : 

Photomicrographs of hog cholera bacilli which developed in different media. All 
were made at a uniform magnification of 1000 diameters, with the Zeiss apo- 
chromatic objective of 3™™ and 1.30 numerical aperature, using projection 
ocular No. 4 and Abbe condenser with largest diaphragm. Orthochromatic 
plates and picric acid screen. 
Plate XIV : 

Fig. 1. Coverglass preparation from spleen of rabbit inoculated with hog cholera 
bacilli. Stainec>two to three minutes in aqueous solution of fuchsin. Mounted 
in xylol balsam. X 1000. 

Fig. 2. Coverglass preparation from bouillon-peptone culture five days old. 
Stained in aniline-water- fuchsin for five minutes, and decolorized in one per 
cent, acetic acid for a few seconds. Mounted in xylol balsam. X 1000. 
Plate XV: 

Fig. 1. Coverglass preparation from bouillon-peptone culture one day old. 
Stained same as Fig. 1 of Plate XIV. Mounted in xylol balsam. X 1000. 

Fig. 2. Coverglass preparation from gelatine culture two days old. Stained same 
as Fig. 2, Plate XIV. X 1000. 
Plate XVI : 

Fig. 1. Coverglass preparation from colony of hog cholera bacilli taken from an 
Esmarch tube, made directly from spleen of pig, fifteen days old. Stained 
same as Fig. 1, Plate XV. X 1000. 

Fig. 2. Coverglass preparation of hog cholera bacilli from agar culture fifteen 
days old. Stained same as Fig. 1, Plate XIV. X 1000. 

16612 H C 13 



Plate I. 




Plate n. 




Plate IK. 




U L C E U AT K D CAK( I U M 



A.f^QeniC. Ll:n.ca:,-.;i,: 3alti 



Plate "R'. 




I u ; r e \ . 




/ 



f 



Plate YT. 




ULCERS IN ILEUM. 



A.Koen* Co. lirhiicduitic. Baltic 



Plate YR. 



■^4i^* 








Plate ^mi. 




\^^ 



-. N ^ V \:V 



HE MORRHA( VIC HEART 



Plate 




f Q.Marx fecit 



HieniCQ.lirhoMOitic, 



COLLAPSE AND BRONCHO -PNEUMONL'l. 



Plate X. 



Fio.l. 



'A 

n 



3 



v-^^ 



Fig. 2. 



(*> 



-*>• *^ 



»^> 



0^ 



a 



e.AIarx fecit. 



HOG rHOLP:F^A BACILLI 



Plate XJ. 




c^ 



Fio.l 



Fig. 4. 



Fro. 5. 



Fjg.2. 



Fic3 



G.Marx fecit. 



CULTIVATION OF HOG CHOLEHA HACILIJ. 



Plate XII 




CT.Marx- fecit 



A.HaeniCo.liThocdus:!:. Saltitr 



CULTIVATION OF HOCi CHOLEKA BACILLI, 



Plate inr. 




DIAGNOSIS OF HOG CHOLERA BACILLI- ( RABBIT 



plate xiv 
Photomicrographs of Hog Cholera Bacillus. 






^-; 




^ *#> 



'^ 



/ I' 



v% 




COVERGLASS PREPARATION FROM SPLEEN OF INOCULATED RABBIT. 



•T* • • 






\ / * . . • . . • \ 



« 



■^ 



^ ' I . 



\ 



• \» 



I 



% / 



Fig. 2. X 1000. 

COVERGLASS PREPARATION FROM LIQUID CULTURE FIVE DAYS OLD. 

PHCrO- CHAVURE CO. NY. 



I 



PLATE XV 

Photomicrographs of Hog Cholera Bacillus. 



b 





« •v.* 



Fig. 1. X 1000. 

COVERGLASS PREPARATION FROM LIQUID CULTURE ONE DAY OLD. 






i -.i' •' - 



#^' 



♦ *': 






% 






Fig. 2. X 1000. 



i- 



COVERGLASS PREPARATION FROM GELATINE CULTURE TWO DAYS OLD. 



'HOTO ORAVURF i; O. N. 



PLATE XV 

Photomicrographs of Hog Cholera Bacillus. 



\ 

} 





Fig. 1. X 1000. 

COVERGLASS PREPARATION FROM ROLL CULTURE (eSMARCH TUBe) 
FIFTEEN DAYS OLD. 



■j • K> 



( 













Fig. 2. x 1000. 

COVERGLASS PREPARATION FROM AGAR CULTURE FIFTEEN DAYS OLD. 



PHOrO-GRAVURE CO. H 



INDEX. 



Page. 

Agar-agar cultures 08 

Attenuation of hog cholera virus by heat 107 

Bacillus of hog cholera, description of G3 

Bacteriological observations 38, 58 

Biology of hog cholera bacilli GG 

Brine, vitality of virus in 88 

Burial of carcasses 126 

Butyric bacilli in hog cholera cases 58 

Buzzards as carriers of disease 01 

Calomel, effect on swine 136 

Carbolic acid as a disinfectant 88 

crude, as a disinfectant Dl 

Cathartics, effect on swine 135 

Causation of hog cholera 03 

Chloride of zinc as a disinfectau#. 90 

Complications in hog cholera 54 

Contact with the sick producing hog cholera 51 

Corrosive sublimate {see Mercuric chloride) 88 

Cultivation of hog cholera bacilli GG 

Cupric sulphate as a disinfectant 90 

Denmark, swine disease in 181, 183 

Detmers, Dr. H. J., investigation of hog cholera 28 

Diagnosis of hog cholera bacilli 06,09 

Digestive tract as a channel of infection 105 

Diseased viscera, feeding to swine. {See Feeding.) 

Disinfectants, effect on hog cholera virus 8" 

use of 131 

Distribution of hog cholera bacilli iu the body 05 

Drying, effect on hog cholera bacilli 78 

Dysentery, relation to hog cholera 122 

Etiology of hog cholera. {See Causation.) 

Feeding hog cholera bacilli to swine 107 

viscera to produce the disease 50, 105 

Food as a means of infection 105 

Fowls, effect of inoculation on 73 

France, swine disease in 18G 

Freezing, effect on hog cholera virus 7G 

Gelatine cultures of hog cholera bacilli 07 

Great Britain, swine fever in 173 

Guinea-pigs, inoculation disease in 73 

Heat, effect on hog cholera virus 75 

Hemorrhagic lesions 34, 52 

History of hog cholera in the United States 9 

investigations l"! 

195 



196 

Page. 

Hog cholera, bacillus of .".' 63,(36,75,78,80,87 

causation of «)5 

history of investigations concerning 14 

introduction and spread in the United States [) 

or allied diseases in France ISO 

Great Britain 173 

Sweden and Denmark 181 

prevention of 26 

produced by feeding 50, 105, 107 

inoculating pure cultures of hog cholera bacilli.. . 55 

treatment of 25, 135 

Hydrochloric acid as a disinfectant 91 

Illinois, investigations iu 110 

Infection of swine, modes of 105 

Inoculation experiments. (See Preventive inoculation.) 

of small animals with hog cholera bacilli 60 

Iodine as a disinfectant ' 89 

Isolation iu hog cholera 123 

Klein, E., investigations in swine diseases 177 

Law, L>r. J., investigations iu swine diseases 19 

Laws with reference to hog cholera 127 

Lime as a disinfectant 03 

Lundgren, Dr. J., investigatious of 185 

lAiugs, infection by way of 112 

Lung lesions in hog cholera ? 54 

Marseilles, spread of swine diseases from 188 

Maryland, hog cholera in ^ 50 

Nebraska, investigatious in 116 

Pathological action of hog cholera bacilli 113 

Pens, vitality of virus irx- — -- 86 

Permanganate of potash as a disinfectant 89 

Pigeons, iuoculatiou of 73 

vaccination of, with sterilized cultures 155 

Plates, description of 191 

Fost-mortem appearances iu hog cholera 34, 39, 59, 106, 107 

Potato cultures 68 

Prevention of hog cholera 26, 123, 170 

Preventive iuoculatiou of swiue by feeding 151 

with small doses of strong virus 139 

with sterilized cultures 150 

Prevention of swiue fever ^ 170 

Public health, relation of hog cholera to 120 

Rabbit, disease produced by feeding 72 

Rabbit, inoculation-disease in 70 

Snow, Dr, E. M., investigations of 17 

Soil, disinfection of, with lime -^^ 

vitality of hog cholera bacilli in 80,86 

Spores, do hog cholera bacilli produce 101 

Staining of hog cholera bacilli 65 

Streams distributing virus 126 

Subcutaneous iuoculatiou of swiue 109 

Sulphate of copper. {See Cupric sulphate.) 

Sulphuric acid as a disinfectant 30 

Sutton, Dr. G., investigations of swine diseases 12, 14 



197 

Page. 

Swedeu, swiue diseases in 181 

Swedish and Aiuericau liog cholera, comparison of 185 

Swiue fever, jiost-moriem lesious in 176 

symptoms of 174 

Symptoms aud post-mortem appearance in hog cholera 33 

Table of hog cholera epizootics in the United States 11 

Tables showing vitality of hog cholera bacilli in the soil 81,83,84,85 

Treatment of hog cholera 25, i:i5 

Typhoid fever, relation to hog cholera 121 

Ulcerative lesions 35,53 

Vacno cultures 69 

Veins of swiue, inoculation into .•. Ill 

Vitality of hog cholera bacilli in the soil 75,80,86 

Virus, attenuation of, by heat 167 

Water, life of hag cholera bacilli in 76 

o 



^ 



^ 



